There won't be a 7nm Vega gaming card because that's what Navi is for. Navi is replacing Vega as the gaming architecure, and replacing Polaris as the midrange product; Polaris 30 will still exist, but it will be classified as the entry-level product. Of course there is scope for a gaming card based on Vega 20, but I doubt it would be any good. There's also talk of a "Big" Navi 20 which might be the 2019/202 Instinct card, or might be the big gaming card.
But we have Arcturus coming in 2020 which is where AMD will start looking at getting back into the high-end gaming cards.