Perhaps, but his track record as of now says no.
He's an adequate first baseman at best, and though I haven't seen him in the outfield, I'm guessing he's below average. Walker also isn't fast and doesn't have much of an arm, which means even in the outfield, the only possible spot might be leftfield. He can "play" two positions, but so can guys like Pedro Alvarez, who is still looking for work. Walker was going to have to make the majors largely on his bat, and that wasn't anything terribly special at AAA.
This is probably true, but Walker may get a shot as a back up first baseman/DH somewhere in the bigs. Playing LF last year may have hurt his batting. He was a solid stick the year before in AAA.