You think his career is stalling? I think he's developing fine. There are stumbling blocks, especially when you come to a new country, with new expectations, language, and a complicated system to pick up. He's still one of their leading goal scorers. The guy spent one year in Rennes, one year in Dortmund (where he did very well), and now is entering his second year in Barcelona....if anything, he's progressed too quickly and Barcelona rushed his transfer (and so did he) a bit earlier than I think he was ready for but being in Barcelona is one of the better places to iron out the major flaws in his game.
I think a lot of the rumors of him leaving are also to open up a new round of juicy Neymar speculations on his comeback. I don't think Barcelona are stupid enough to let him go, but with their current leadership anything is possible. If he's available, every club should move heaven and earth to get him.