I was way more excited about a Tekken-gameplay crossover than the SF kind of game, so this news are pretty sad. At least it's not cancelled yet, but I wonder how many times it has been rebooted internally.
I don't think the game has ever been in some development hell, it's just a question of when it'd be viable to take the idea into proper planning and production.
Akuma's precense in T7 does seem like the team could start venturing into this soon.
My guess is that Akuma in T7 is testing the waters/laying the groundwork for this title.
Also means that TXSF, when it eventually appears, could be a 'canon' entry into the series from a narrative perspective, on the basis that Akuma gets the ball rolling.