The SR platform is so robust, 10 mm and .357 Sig would be easily do-able.
.357Sig, yes, but 10mm Auto, not so much.
The absence of an "SR357" probably has more to do with perceived lack of market demand than anything else. The round continues to garner LE contracts, but based on talking to the management at a few LGS's, civilian interest in the round seems to be dropping.
OTOH several older .45ACP auto pistol designs adapted to 10mm have a reputation for beating themselves to death with extended use of full-power 10mm ammo (e.g. Colt Delta Elite, S&W 1000-series). The G20 was designed around the 10mm cartridge and doesn't have this reputation; the G21 is adapted from the G20, not the reverse.
I don't think it's reasonable to assume that the SR45 could be adapted into an "SR10" until it hits the market and some expert 'smiths have a chance to analyze it.