People stop buying Call of Duty. It's sad, but I'm pretty sure that's what would happen. They would basically consider it the end of the series.

I think WiiU would have sold a shit ton of consoles and maybe have even been declared the winner since GTA V really is that big... It would have pushed the sales initially therefor getting more third parties to come in and support the console which would have given Nintendo more time to release their games... It would have also shown the gamers that Nintendo really was serious about third party and the hardcore audience

But that didn't happen so, the poor console will be struggling for a while if not forever and also it probably wouldn't have sold as much as it did anyway

1.) This would probably be the worst selling Grand Theft Auto in the series' history.
2.) Wii U sales will surely go up, although not for a sustained amount of time. (Until the next GTA.)
3.) There would be even worse complaining than we had when Bayonetta was announced exclusive to Wii U.

Will this ever happen? Lol, no.

The same thing that happened when RE remake and zero where exclusive to gamecube(and even RE4 for a while). RE was bigger than GTA at that time. But was not enough to change GC fate.

It will be a METAGON MASTER BLASTER...

But...

Yeap... but.

The chances are near 0%

With the aggressively reluctant nature of gamers to buy consoles outside their box, they would boycott the Wii U and try to force Rockstar to release the title on their preferred consoles. It's the same thing that is happening to Bayonetta. Nintendo is funding the project, it will NEVER be released on another console, but the "fans" of the series are refusing to buy a Nintendo console to play a game they love, and are treating Platinum Games awfully. So I believe the same thing will happen, just on a much larger scale. But there would be a small uptick in sales from those people that generally just don't care what console it is on.

GTA is a major series that would have a major impact. We saw it when Xbox 360 secured a same day release of it and FF13. Microsoft effectively took half of the PlayStation market. If Nintendo secured GTA exclusivity - and this could only realistically happen by buying Take2 - many GTA fans would by the system. Easily 10 million or so. To work well, however, it would have to be paired with proper marketing and ideally some other titles that compliment GTA, such as COD(not exclusive, but properly supported and promoted).

It would probably sell millions of WiiUs on its own. I know I'd buy one (if cheap). But, it would also mean GTA loses millions of sales.

millions would switch to Nintendo and thus 3rd parties too

securing GTA would make Nintendo very competitive. it really is that simple.