I don't have any hard numbers, but there's been a massive uptake in 1.9 since the release of 1.9.2. I've been doing all of my projects in 1.9 for a while now, and I very rarely run into compatibility errors.
Like I said, I have no numbers, so fundamentally it is just a guess.
And of course this is just a guess too - "It's been long enough now that lots of people have moved their projects over."
Maybe we could step from wag to anecdote if there has been a straw poll at some recent Ruby conference asking which version the attendees were using?
And I'll grant that you're part of the community on your say so.
But being "part of the community" doesn't magically enfuse you with knowledge about what proportion of the community is using what version of Ruby. To be educated about that is to count the numbers.