You pretty much just lose all of the gameplay benefits you originally paid for. I think that the price for Premium should be brought down substantially to accommodate the changes, seeing as your only benefits now are purely aesthetic or only visible to you.

Personally, I am okay with the changes. I have never liked pay-to-win, and only bought Premium because it was almost necessary in order to stand a fighting chance. I'll happily be giving up my Premium subscription so that I may play fairly among all the other players at no additional cost to me.