I don't see why it would be unlikely. The standard identity smartcard (DoD PIV card, openPGP card, etc), like the standard credit/debit card, uses the same physical and electrical interface as a SIM (because a SIM is also a standard smartcard): the ISO7816 pattern. Dual-SIM phones are pretty common — even Apple has one! — and there's no technical reason you couldn't make one of the SIM sockets hotpluggable and present it to the applications on the phone instead of to the cellular module.