No way this leak is real. The two free characters and inclusion of Q are proof. Capcom isn't giving away characters and the fact G's story mode costume resembles Q's default costume in my mind means we're pre-Q in SF lore canon.
The only credible SFV leaker to date has been Flowtron.
Capcom has given away quite a lot of free content in SF5 when you think about it - so I could believe that part of it, tbh.
What I don't believe is that this season won't have a single SF2 rep - they are
surely going to do Honda to reunite the original 12 world warriors. He's the last one now. And I just don't see the point in Q - he's just a Balrog (Boxer) clone/alike when it comes down to it, so they'd have to change him significantly... which is what it seems like G is gonna be, similar ideas executed in a very different fighter.
This feels a lot like a decently educated guess, though. Sodom and Viper seem like likely inclusions and obvious choices - we know Sodom was in planning/development before even the vanilla game was released, and Viper is the only character of import who isn't playable who mysteriously has an all-new design in some character story modes - plus her mechanics just seem like they'd naturally lead to quite an interesting incarnation in SF5. Makoto is the highest ranking character from the popularity poll not yet in SF5. I feel like those three "fit", plus Honda - which'd leave space for two more.