yeah we cannot say that bitcoin is already mainstream because there such people who know what is bitcoin really are, and most of people are didn't yet know the bitcoin and also more people more likely to used their own currency than bitcoin, because they though that bitcoin is NETWORKING :3
The only way bitcoin could be assumed mainstream when there is a significant amount of people enough to stop transacting in any other currency except bitcoin. The amount of people who would desire this evolution would be enough to cause a change/effect loss in the market if they did not buy anything despite being potential customers of this organization/business/etc. As of now, bitcoin stands
not mainstream.