Yes, I also think that Jesus knew quite well the situation of women when he said that the only permissible divorce was for sexual immorality. I would think that if abuse were a reason, that He would have said it. Then again, "abuse" runs along a spectrum.
Unfortunately, the way people act, I feel like sexual immorality in marriage is so common that the question of whether to divorce on the basis of the abuse wouldn't even have to be asked a lot of the time.
I think that it's
highly unlikely that an abusive husband would remain faithful to his wife for years after being separated. I don't think she would have to wait.
However, sometimes--maybe even a lot of times--God calls us to go above and beyond and wait for Him to do something great, by faith. Even if there are biblical grounds for divorce, that doesn't mean that people have to leave. I know a woman who has been waiting for years upon years now, for her husband who she has every reason to forget, because God spoke a word to her about it. In the meantime, she's helped many divorced couples reconcile.