Well with the feeling being mutual, you have a chance, but not just yet. I recommend you wait it out because if this guy's girlfriend treats him like crap, then he's sure to move on to someone else if he had the mind to.
If he does, don't go straight into it, just wait it out a week or so - he needs to recover. During that time, just keep talking to each other, keep communication up. And give him some sort of signal after say a week to show you are still interested.
If he doesn't ditch her, then just keep talking to him as friends and he might gather more interest into you with the interest in his current girlfriend diminishing.
Either way, things could happen. Good luck with it all :)