There is no level cap as far as I know, but as you level up it takes more xp to gain another level, so people generally ended the game at around level 45-52, exceptions being with Ariana at the end being level 17 (trying to set a record for the lowest possible level finish) and Lews, who used an old resurrection trick to reach level 59.
EDIT:Also, the game doesn't provide so much of a challenge (although the challenge is way better than many games), so you could end the game with lots of skill points extra, although at the beginning there are quite a few vital skills so you'll probably be using your skill points more near the beginning.
