Street Fighter V, while praised for being a great fighting game, came under fire early due to… well, not having much game there. Story mode didn't come until later, and so many features were missing at launch.
If you feel like you've missed the train now the game has gotten its act together, perhaps don't. It seems this game is going to have a massive tail, or so Capcom claim. Famitsu (via Event Hubs) recently spoke to exec. producer Yoshinori Ono about the game, and he explained the game has a plan for years down the line. He said:
It's not just a 1-2 year thing. We're looking pretty far ahead … We've planned out as far as 2020 or so.
Now, this doesn't preclude a Street Fighter VI coming out before then, just that there might be support for a little while after while V is phased out. At the same time though, with the competitve scene such a large part of the game's plans now, it probably benefits Capcom to keep one standard for as long as possible. I think it would be a safe bet that the game has a fair few years in it yet.