60 cards breaks the rank 3 card limit (still only 1 4-5 star card). You can't currently break the 4-star limit, though that might be because you can't have 90 cards (since there aren't that many yet). I'm not sure they'll ever allow unrestricted access to 4-star cards or not. It would start getting a little odd having nothing but fantastic cards, but who knows? They might make new tiers and card values to allow more room.