I'd love to see 2D spites again like KOF 13.

Though I think they'd be worried the visuals would hinder its sales, so more realistically I think it'd be something like this.

Fei-Hung said:

I don't know why, but it seems to take longer to make these games too where other games pump out several games with equally as deep mechanics or more, whilst street fighter struggles. 

It's probably true that 3D would make the game take longer than 2D. But which games do you feel took longer?
I haven't compared the release dates, but Street Fighter 4 and 5 kept getting updates with new seasons, characters, mechanics, balance changes, etc every year or so. Which is similar to how they handled Street Fighter 2 with a lot of new version releases.