I think a resort, or even just a nice hotel, would be a complete failure. And the cost of that failure would likely result in a massive slowdown of "in-park" development (if not a complete stoppage) for numerous years. And possibly significantly higher prices at the park to compensate for the financial failure of the hotel/resort.
Carowinds has improved dramatically, but it is still a 1 day park (or maybe 2 days so the kids can spend a full day at the water park now). It's also a nice park for locals to go spend an evening or afternoon once a week during the summer, like me. There's nothing else in the immediate area of Carowinds, so we never hang out near there, we go home. It's a boring and ugly industrial neighborhood. The Carowinds neighborhood is basically a warehouse/truck stop area. It's a place for a a couple budget hotels, nothing more. And those budget hotels are already there.
Who is going to stay at the Carowinds Hotel in November? Who is going to stay there in March? Who is going to stay there in the months between?
And truthfully, I think the place would be mostly empty in July also. Why? Because if I was planning a family vacation, I'd want to go someplace fun (which Carowinds is) but I also want to someplace beautiful and relaxing, with a large array of recreational activities. The Carowinds area is neither beautiful nor relaxing... and there's nothing else there besides Carowinds. Nothing.
If Carowinds was on a great beach on the coast? I think a resort would make sense. If Carowinds were sitting on a lake right outside of the Great Smoky Mountain National Park? I think a nice hotel would likely make sense. If Carowinds were near a number of other popular amusement parks, each with unique things to offer, and people wanted to spend a vacation going to all of them? I think a nice hotel would make perfect sense.
Carowinds is in a grimy industrial zone with nothing else to offer vacationers.
If (for some crazy reason) I decided to bring my family to vacation to the Charlotte area, where would I book our room? I'd book it uptown. There's museums. There's professional sports. There's good food. There's live music. There's art. There's Imax movies. There's bars. There's public transportation. There's things for kids and adults of all ages to do (rain or shine, summer or winter). And it's a pretty area. There's fountains and sculpture and architecture. And there's quiet green areas. It's a nice area you can walk around enjoying yourself, just simply walking around. And there's already large convention centers for events.
I'd spend 1 day of that vacation (2 days if young kids/water park) at Carowinds. And then I'd leave the Carowinds neighborhood and immediately head back to Uptown Charlotte after exiting the park, and for the rest of my time in Charlotte.
Even if Carowinds had:
1. A dive coaster
2. A wing coaster
3. a couple of launch coasters
4. a couple more wood coasters
5. a whole bunch of more flats, dark rides, and smaller attractions
6. a log flume
7. a golf course
8. tennis courts
9. etc etc etc
Would I then bring my family to spend a week at the truck stop where Carowinds is located? No. I'd still go to Cedar Pointe. Why? The beach, the scenery, the air, the relaxation... all the things that make that area a smart place to build a true resort that the Carowinds area does not have, and will never have. The Carowinds area is never going to lose it's industrial truck stop atmosphere. And they can't move the whole park to a true vacation area .
Budget hotels + the campground and fast food completely fill the need of the few coaster enthusiasts who make a road trip to get their Fury credit (and spend 1 night in the area). If Carowinds keeps improving like they are, then Carowinds can expect to keep seeing the attendance rise, mostly from locals. More enthusiasts will be making longer drives also (and then move on to Dollywood or King's Dominion the next day). And they'll keep having increasing season pass sales. This should be the objective for Carowinds: reasonable growth. Trying to make a resort area out of truck stop/industrial area would be a costly mistake.
Because families on vacation are going to still go to Orlando instead. A hotel in the parking lot of Carowinds is not going compete... at all. People aren't going to want to stay there for a week or two.
Hotels need relatively steady occupancy rates in order to staff properly (and pay those employees). Staffing a hotel/resort with a significantly fluctuating occupancy rate is a nightmare, and a recipe for very very unhappy guests (read the reviews of the hotels that are near Carowinds currently). Trying to make a nice hotel, where guests only stay for a single night, is a total fail. There are hotels on freaking Maui that struggle to keep occupancy rates steadily high ( Carowinds parking lot?

). Nobody flies to Maui to just stay for 2 days and 1 night (the airfare is way too high for short trips like that).
Who's going on a family vacation to Carowinds when they can go to Cedar Point? Who's going to Carowinds when they can go to Orlando? Who's going to Carowinds when the can go to the coast? Who's going to Carowinds when they can go to to the mountains?
And who's going to stay in the industrial neighborhood of Carowinds, when they can stay in Uptown Charlotte (an easy 15 minute drive from Carowinds)?
And this is exactly the huge benefit that Carowinds has over many other parks. It's so close to uptown Charlotte, it doesn't need to build hotels. It doesn't need to build good restaurants. It doesn't need to arrange evening and late night entertainment, or build those venues. It doesn't need to be a full resort. It can solely focus on building the best amusement park rides in the region. Carowinds can leave the building and capital expenditures of hospitality to other companies and investors. They only need to build rides and attractions (and fry up some funnel cakes). And focus on the in-park experience like a laser beam.
Do I think Carowinds might want to add some sports facilities, or other forms of entertainment to do around the periphery of the park? Sure.
But I don't think building nice hotel/resort would be a good idea... I think would almost certainly degrade the quality of what happens within the park as a result of this terrible business idea.
But I would say, that IF (and only if) the budget hotels near the park are regularly at maximum capacity, then maybe Carowinds could partner with a budget hotel chain and build another small budget hotel near Cabela's or something. I get the feeling that the hotels already in the neighborhood are not doing very good business already, from the feedback I've heard.