It does seem unlikely that after only getting dribs and drabs for years, that suddenly there's a massive avalanche of episodes coming our way in the next few years.
Although I would certainly love to be proven wrong.
My understanding is that Phillip Morris has been actively hunting down lost episodes of Who
and other BBC shows in places around the world where nobody ever checked before -- or rather, where nobody replied to earlier requests about lost episodes. So if that more extensive effort to track down lost episodes has only been going on since relatively recently, then it could indeed be that they've been out there all along and only just been found. So it's at least possible.