Judging by the number of attendees at conferences, Groovy is like the tide rolling in rather than like a meteor streaking across the sky. The number of attendees at my Groovy presentations keeps rising every year, but not by staggering amounts.
I would say that there are people available, but they're not uniformly distributed. You can do a search http://indeed.com/jobtrends and see how many developers you find.
Of course, the good news is that any decent Java developer can learn Groovy and do well pretty quickly. You can therefore make Groovy developers almost as easily as you find them.