I do not believe 2015 will be the year Bitcoin 'goes mainstream'. Yes it will be talked about, more people will use, hold or trade it and more merchants will accept it. But we are far, far away from big scale adoption... Honestly, I do not think any 'common folk' will actually use this for at least another 3 years. Let's talk again in 2018-2020. If Bitcoin still exists (and I hope so, since I'm a longtime holder and believer) by then, it will be widely accepted and price will have risen also. But for 2015, I predict more or less the same path we've started in 2014. Up, down, left, right, adoption, repeat.