I don't think anyone other than probably Sunny Leonne made their career in Bollywood after BB. But I feel that she would have made it even without BB.
BB will only give them a short term publicity and not much. The winners also haven't done much. TM has already mentioned about Gauhar & Gautam, who apparently had tremendous fan following but have hardly done anything remarkable yet in Bollywood.
Both Rahul Roy & Ashutosh, the first 2 winners, have disappeared from limelight. Vindoo bought himself disrepute in the cricket betting scam. Shweta resolved her personal issues and got remarried. Juhi got a baby and now back in TV serials in motherly roles. Urvashi, regarded as one of the best winners, was abused during Season 8, for her blog and Prince is back to roadies. No one made any mark in Bollywood.
Even Arijit Singh became a star after much hardwork and a 10+ year wait post Fame Gurukul.
It will be just an unreasonable expectation to hope for stardom post BB. I think BB can give the contestants only some fans and that's about it. That's the harsh reality. For stardom, or even some success, they have to slog and work hard, and there is no substitute for hard work, with some luck factor.