Mr_No on 29 August 2016
http://www.ign.com/articles/2016/04/14/grand-theft-auto-onlines-microtransactions-are-big-business
They're profiting pretty well with the Shark Cards, so they'll milk the hell out of GTA Online until it's time to announce the next game. I don't think they'll let the momentum of this game die out with like 1,000 people playing it daily. My guess is they'll announce something by next year and keep the interest alive amidst delays with trailers.
