"but tantalum is cheap. Until it has to go into every memory...

"but tantalum is cheap. Until it has to go into every memory chip in the world"

Negative.

It has already been going into billions of tantalum capacitors for over 5 decades. Digital circuits are full of them. The quantities needed in the manufacture of a capacitor far exceeds what would be used in a memory device. Besides which, it won't be happening. The Fujitsu - Panasonic technology is too expensive for other reasons that I have already articulated. It is therefore likely to remain a niche alternative to EEPROM. That is at least until something better and cheaper comes along (e.g. WBT's ReRAM), after which it will be discontinued.