Rules say gi is optional, grabbing shirt or t-shirt is illegal. Kinda vague. I think you are allowed to wear them and they can't grip them, but I have seen a trend of allowing your opponent to grab your pants if you choose to wear them and you can't grab them. However you are allowed to grab your own shirts, just not his.
I was wondering about this as well. I don't know if Eddie wants to leak this info yet. Along with rash guard. I'm pretty sure he'll go rashie, board shorts, knee and ankle sleeves. We'll see.