Seth Killian recently clarified on the Capcom Forums why Street Fighter IV didn't have bonus stages, and Christian Svensson also later jumped in on a possible sequel or re-release to Capcom vs. SNK 2.
Why haven't newer Street Fighter games featured bonus stages?
I think Seth or some of the older Street Fighter players can chime in here but wasn't it due to a mix of arcade operators wanting max earnings during a day so they wanted the most vs. play possible so they asked to include a dipswitch to turn off bonus stages all together to make the most money possible? — Toshin
Seth: Toshin is right that bonus stages are not the friend of the arcade operator, who loves nothing more than separating you from your quarters (or yen) a.s.a.p.
The Street Fighter 4 team definitely still loves the bonus stages, however. They weren't added into the console version primarily due to time constraints. So much core game that you have to get JUST right means sometimes the bonus fun doesn't make it across the finish line.
Would it be possible to make a sequel of Capcom vs. SNK 2 on XBox 360 and PS3, or even to have CvS2 as a downloadable title?
Sven: Theoretically, though it would take new agreements with SNK and significant development to do the porting to those platforms. Given the amount of fighting games on our plate lately, I don't see those happening in any near term timeframe, but we'll see.