If they launch late 2020, the next xbox will be ready too. There won't be a year's headstart or anything, it will most likely be an aligned launch like this gen.
Sony can't go a year without any shows or any announcements of any sort. If TLOU 2 is a holiday 2019 game, I can see the next ps5 launching early 2020 giving them a 6 months head start on the next xbox.