It'll take them six months to produce a reasonable facsimile , but then they probably don't have another feature release planned for that amount of time anyway.
Personally, I think the Xobni guys are fools for refusing the offer. If Microsoft are interested in acquiring the technology, then they're almost certainly going to become a competitor now the offer is refused. They could do far worse than selling out for 20 odd million in cash and stock, spending a couple of years working for Microsoft while their stock vests and then going on to the next big thing. Instead they've got themselves an uphill battle in which they are running very barely ahead of a corporate juggernaut.
Well whatever happens, it should be entertaining.