It was a rumor about a month or two ago and I don't remember where.
At the time it made more sense for the Epic to go to Boost as a compliment to the Optimus Black, but if we get the 3D, the Epic would be a good keyboard based phone to compliment that.
Either way, I haven't heard any more about any of it and frankly, after what VM has done lately (which is nothing) and how the rumors have been panning out, I don't trust any of it. I think Sprint is in turmoil and the rumor mill is working overtime with people speculating on anything and everything. We know VM has to do something soon, it's just a matter of what.
I wouldn't even be surprised if we see NONE of these phones on either carrier and instead end up with the One V to hold us over until sometime around New Years when we get one of ZTE's budget LTE phones (which they showed off in January). Wimax on Virgin makes sense for us, but not necessarily for Sprint, it means supporting that system just that much longer.