Considering the significant startup performance improvement (especially for mods) they bring and that ongoing development of Factorio will soon be coming to an end (visible sadness), will these be formalised into stable settings for 2.1?
Not likely. The sprites one forces runtime-generated mip-maps instead of the custom created ones the graphics team created. The prototype caching while not having any known issues was not deemed worth turning default-on.
If you want to get ahold of me I'm almost always on Discord.