I dunno. I have mixed feelings.
A 9th season....I thought 8 was pushing it, but it worked OK. Adding a new cast member for season 9? Touchy. Depends on his position. No way I'd want him coming in above (Lt.) COLONEL Carter. Also depends on whether or not they're calling it the "last" season or holding out for seasons 10,11, etc. If they're freshening up to go long, then fine. If he's just coming in for the last hurrah, then it doesn't do much.
Also gotta wonder about the role. Obviously he can't be Crighton, a character I very much enjoyed. So how subdued and/or military will they make him?
Throw me a bone. Have him knocked out or sleeping in one episode and when they wake him up, he says "I dreamt I was on a ship...a living ship." That would be a nice cross-touch for the fan-boy in me.