I worked the overnight shift at MLBTR and just woke up after sleeping for a few hours, so I'll just link there for a summary of everything that went on with Neil Walker while I was out. Basically, with Ben Zobrist off the market, there's suddenly a ton of noise about Walker, the kind of noise that starts happening when a player is about to be traded. (But maybe Walker isn't. I don't know.) The Angels, Mets and Nationals have emerged as possible trade partners (although the Nationals' interest appears to be less serious than that of the other two teams).
The Pirates need starting pitching, of course. Separate from the Walker rumors, the Angels are reportedly willing to trade C.J. Wilson, Matt Shoemaker or Hector Santiago; Santiago would be a good fit for the Pirates, although he's probably too valuable for the Angels to move in a one-for-one trade.
The Mets could deal Jon Niese, with the idea that they would then use Rafael Montero in their rotation until Zack Wheeler returns from injury. That would, however, be a depressing trade for the Pirates to make one-for-one -- Niese isn't as talented as Walker, and his 2016 salary of $9 million is almost as high as Walker's projects to be. Of course, the Pirates have thrived recently on making somewhat depressing-looking pitcher acquisitions and then turning them into gold, but one would hope there would be a better way of making an acquisition like that than by trading an actual good player.
Ironically, the Mets already have a good young second baseman in Dilson Herrera, who they initially got from the Pirates in the Marlon Byrd trade two years ago. He's big-league-ready or awfully close. If the Bucs were able to get him back in a trade for Walker, that would be terrific.
So your guess is as good as mine at this point. What does seem clear is that the rumors surrounding Walker have gotten a lot louder. It wouldn't surprise me if there was a trade today.