It's totally impossible to answer this question.
For one thing, people who know he's still alive must first know that he was supposedly killed. We've no idea how many people know that.
Next, the Doctor is a time traveller, so even if someone who knows about Lake Silencio meets the Doctor alive, they may or may not know that (for the Doctor) the meeting is after Lake Silencio instead of before it.
Furthermore, the episodes of Series 7 have made it unusually clear that the Doctor is doing all kinds of things (taking up many, many years of his timeline) that we aren't being shown. Since we're not being shown, we've no way of telling who has found out about his survival or how they found out.
As of "The Power of Three", we know that UNIT wasn't even mildly surprised to find him alive at the Ponds' house. We don't know if UNIT knows about Lake Silencio or if they'd any clue about where in the Doctor's timeline the relevant events occurred.
More than anything, faking is death was really just a way to get the Army of the Silence off his case. They'd already failed to kill him twice: once with the Pandorica and the second time getting River to kill him only for her to resurrect him. Given this third attempt, putting River in a spacesuit and forcing her to do it, it must've been clear to the Doctor that the only thing that would stop the Silence from hurting the people he loved (Amy, Rory, River) to get to him was for them to believe him dead. It's only really them who he needs to convince, and if they hear of him alive in the future they can just assume that it's an earlier version forever destined to meet his demise at their hand. Maybe, in the same way as the legend of the Doctor spread, his "death" will spread across the Universe and afford him a bit of renewed anonymity, but that's just speculation.