Without any serious trend observations, here are some predictions.
By the end of 2013, it'll be at about 84-85m. By the end of 2014, it'll be at around 90m. After that it'll sell a few crumbs most likely.
But I'm honestly not too sure. Sony seems to be pushing the PS3 strongly at the moment and I'm really not sure how much a sub $200 PS3 would do.
I say it is possible for it to reach 100m but it'll need a lot going for it. It will do at least 90m though, which is great.