Crappy timing =/. I'd buy a used 2015 mbp and plan to sell it when the new 6 core macbook pros come out. Probably won't take too much of a loss.
This is what I would do. You could take a chance on ebay (which does have great buyer protection if things go awry) or craigslist and maybe find a bargain. Use that machine until June or whenever the new ones come out, and then flip it without taking much of a financial hit.