I admire your optimism, but...
Given Gartner point to mass adoption of VR still being some 5 years away, and Zuckerberg has made it clear that FB are in the VR game for the long haul (think, as Oculus VR investor Chris Dixon has said, in terms of Google's 2005 acquisition of Android), I'm not so convinced FB will be making any immediate jumps in any direction, VW-wise.
And when they do, I seriously doubt it will be in the direction of SL / OpenSim. Frankly, both have too much associated baggage (even if OpenSim's is the result of it being seen as sitting in SL's shadow as far as the world at large is concerned - and no, i'm not knocking OpenSim in saying that).
Rather, if FB look anywhere, I'd tend to lean towards them looking at the likes of High Fidelity. Rosedale's start-up just claimed its second round of investment (a further $2.5 million on top of that originally seeded by the likes of Linden Lab, Kapor Enterprises, and Google Ventures).
If nothing else, this puts them squarely on the map as a potential proposition down the road. In addition, in terms of goals, those Rosedale has voiced for High Fidelity seem to be a remarkably good fit for Zuckerberg's initial statements on his long-term aspirations for "social" VR ...
Of course, there is the Ondrejka / Rosedale past to consider (assuming that even is an issue now, severn years down the road), but I'm not sure that would stand in the way of an potential deal, were one to be considered at some point.