Eventually can be a long, long time.
Don't hold your breath waiting for the specific base that you want.
There is just no predictability to this scheme of giving upgrades for old buildings.
I never get an upgrade for something that I want. What good are 14 upgrades for a building I never put up?
Sure, I can disenchant them but even now I have a huge rover supply of spell fragments and things to disenchant.
Have faith charlemagne, that building you want WILL come eventually.