Even if that's the case, 4 months with a player who really wants to do well is better than none! If he plays really well and gets snapped up by another club so be it, at least we have got a good few points and goals from him. If he plays average lets sign him up for the rest of the season. If he plays crap we won't extend.
He might even decide after 4 months he wants to stay, some of our better players don't leave the club even though they may be able to get better offers because they like the team - Hopefully that's the case anyway...