Well most probably it will be some kind of the third party usd on the cryptocurrency version. Like usdt is at the moment and this is due to it being traded versus all the other altcoins and thus raking in a lot of volume. Another one in second place will be bitcoin of course because it's the most mainstream crypto that is growing back up in dominance. Hopefully a new bullrun starts soon and bitcoin will get back up over the 90% dominance again..