Wonder how this will turn out..

Have you tried asking him to stop?

In psychology, we talk about something called "operant conditioning."

The main idea is that if a behavior is rewarded,
then it will likely repeat.

If a behavior is followed by something unpleasant,
then it will likely decrease, or stop altogether.

The two of you used to hit and kick each other playfully.
The playfulness and fun was a reward for that sort of behavior, you see?

So when your boyfriend punches you randomly and laughs, it's possible that he's doing it because he's looking for that same reward. That feeling of playfulness and fun.

You can try to change this, by taking away the reward.

If he punches you, you don't laugh, you don't smile,
but rather, you look him in the eye and tell him that it's not so much fun anymore.

I don't think that there's enough evidence here, to tell whether or not this will turn into an abusive relationship.

But I DO understand your fear.
You could try bringing this fear up with your boyfriend as well.

Ronan has it right, but just remember that you have to stop punching him too, ok? If of course you didn't stop already.
It's strange that you are worried about asking him to stop. :/ Keep an eye open for behaviors that you aren't sure if they are ok or not and talk about them with someone to check.

There are a lot of couples that play pranks on each other, but don't place their hands on each other. It looks like it can get pretty annoying, but no harm is done. It's possibly not abusive yet. Right now it's for fun and as Ronan said, your boyfriend is being conditioned to think this is okay because your not speaking up about it. He's your boyfriend, he shouldn't want to hurt you so telling him what is on your mind shouldn't be as hard as you might be thinking. What I think you should look out for is the mood when he randomly hits you.. I think this will be what will let you know if he's leading towards abuse. If he's bothered, annoyed, upset, followed by a comment.. these types of things will let you know if he's crossing the line. But really, just let him know.

Are you able to fake cry? If you can, cry when he does that next time, but he has to believe its real! While crying tell him he's been hurting you like that in the past. If he believes it he won't do it again. If he does, it means he is abussive and you should leave. If you can't do it then yeah, like Ronan said, use that technique, or just sit him down and talk about it, nothing to be afraid of really.