Will my cat and dog ever get along?

I'm 17 and I've had my dog for as long as I could remember, probably ever since I was 10. I've gotten my cat 2-3 years from now and they still don't get along. We just want them to get along before a really bad fight breaks out or something. They never really go a chance to bond because my mom always wants the dog outside the house (saying 'its and outside dog' -_-) She ALWAYS keeps it on the leash when in the house while the cat roams free, and when she puts the dog lose (which is once in a blue moon) the cat always looks like it wants to just pounce on my dog, how long will this last? or how can I make them become use to each other?