Now that it's (clearly) catching on, I can see Google and/or Samsung re-branding their Pay apps to something else (maybe Google goes back to Wallet?) and including ID capabilities.

Personally while I like the idea of digital ID, never losing your cards, almost-impossible to get stolen, I don't like the idea that if someone (i.e. a LEO) needs to see my information, I might need to hand them my device, and in a some jurisdictions could be considered granting consent to a search. I also don't like the idea of what happens if your phone is damaged or the battery dies and it contains your only identification.