If they're faced with a competitor for investment that leaves the metaphorical door open, they're already one step ahead.
They've made billions. R* just needs to support the franchise at this point, the name alone sells them millions of copies at launch. Considering the traffic/driving in gtav is utter shit, peds are ehhh, there's not a lot of highend NASA level AI going on. It's super fucking violent, and its real fun. GTA is more about the experience/franchise then the code, which I'd say is meh in terms of quality. Some stuff is worse since IV. There's no reason to go to war with the modders, they're good for business. they just have to protect piracy and online, which is fine.