From Jayson Stark:
#Pirates emerging as serious bidder for Justin Upton. More on that and other trade buzz on the 12:30 ET edition of Baseball Tonight!— Jayson Stark (@jaysonst) July 15, 2012
#Pirates so serious about Justin Upton they're sending signals they could include Starling Marte in an Upton deal -- but not Cole or Taillon— Jayson Stark (@jaysonst) July 15, 2012
Stark said pretty much the same thing on the Baseball Tonight hit that he teased in the first tweet; the Pirates are seriously interested in Upton, that they're willing to deal Marte for him, and that they wouldn't trade Cole or Taillon.
I still find it hard to believe that Arizona would make this deal without getting Taillon or Cole (so, just assume Taillon because Gerrit Cole's not getting traded) in addition to Marte, but the implication that I pick up from Stark's comments here is that Marte might be enough to push this deal forward by himself (presumably in a big package with guys like Brad Lincoln and Owens/Locke/Wilson).
The next 16 days are going to be ... interesting.