Wilson Betemit is a streak hitter, who if he gets hot, will help the Tigers a lot. If he doesn't, he is not going to much of factor. It's like flipping a coin. He could either direction, but will unlikely be in the middle.
Betemit has to hit to be effective. He is a far below-average defense player - especially at third base - and on a team lacking range defensively, he only adds to the issue.
But in the bigger picture, is an upgrade from Brandon Inge? Absolutely. Put it this way. There is no way he will be as bad or worse. He is also much better player than Donald Kelly, who would get exposed badly were he to play every day at third base for the Tigers.
As for Inge's future, it's not out of the realm of possibility a club will trade for him - but for virtually nothing in return, and only if the Tigers' pick up his contract other than the required minimum portion. Inge can refuse any trade.
Otherwise, the Tigers will likely release him. The handwriting is on the wall.