Here's what I recommend stockpiling:
*Fuji Velvia 50 (rolls, Freestyle getting in a last batch of sheets soon)
Fuji Provia 100F Rolls and sheets
*Fuji Reala rolls, 120 format
Kodak Portra 160 rolls and sheets
*Kodak TXP 320 sheets
Efke KB25 rolls at Freestyle.
Also some 400 asa fuji and kodak color neg film in rolls.

I feel the most precious and endangered emulsions are Velvia 50, Kodak Portras, and Kodak TXP 4x5 and 8x10 sheets.
I feel that if you buy the above fresh, double seal airtight and freeze, you can use these emulsions for the next 20 years.

Also, put away some slower asa Ilford films as a hedge against what is sure to be price gouging once kodak and fuji drop from the market. PanF, FP4+, and Delta 100.