Yes, on the positive side, this is a no-brainer. Polanco is no longer an offensive positive at third base, despite his amazing defensive skills. Polanco's also making a nice chunk of change, which the Phillies would love to move out. If the Orioles want him, this is a move the Phillies can do regardless of whether or not they think they still have a chance or not, as Fontenot and Wigginton can man the position adequately for a team that thinks it can win, now that the Phillies are totally healthy otherwise. For those of us who think it's time to sell anyway, getting a body or two back for a guy that we would be happy to not see on next Opening Day is exactly what we should be doing.
Before you get too excited though, remember that Polanco is not totally useless, nor is he worth literally "whatever they give us." Giving him away to Baltimore, just to insure we give him away for a body, is not good GM work. I want this deal to happen too, and I don't think the asking price should be absurdly high, but you don't "give away" a guy in your line-up.