Not sure if you've read the first two portions of the White paper for 2.0 but they show that feeding monsters will become more complex; with different element monsters getting substantial boosts (or not suffering inefficiencies) from eating specially formulated foods.
Seems grain will be a factor in production of those special foods and I've yet to see mention of expiry/spoilage on grain; so I'm just stacking hard; and don't plan on selling any even when the option to do so rolls out.
That said, if I start 2.0 with heaps more than I'll ever need, and have the option to build a silo and dump a heap into a liquidity pool, that'll work too :)