While Hollywood Reporter is out with a story about Chuck Lorre trying to put together a "Sheen-less" Two And A Half Men reboot. At the same time, TMZ is quoting an unnamed source that says "There really is a good chance the show won't come back."
Those two stories aren't mutually exclusive, but CBS is running out of runway to make a decision. Their advertising upfront meeting when they reveal the Fall 2011 schedule is May 18. Any decisions made after that date would cause them all sorts of headaches.
I think the likelihood the show doesn't come back in some form is low, simply because it doesn't have to do as well as it did with Sheen, just well enough to make it better than one of CBS's other sitcom alternatives. It would seem to me to need to be a huge mess for CBS to at least give a revamped show a shot.