At some point in the not too distant future, it seems rational that a few equipment manufacturers will band together to create a facility to build vacuum tubes. It isn't rocket science (it's actually pre-rocket science). Those who choose to use vacuum tubed equipment can pay the price of their decision.
That's not to say that there will be a wide variety of tube types, just that a handful of tube types would be created to satisfy demand in those manufacturers' electronics offerings.
Remember what happened to vinyl production to satisfy demand.