I guess there were Cheronians offworld when their planet was burning rubble and dead cities in 2268. Makes at least some sense. Any planet where individuals can live for 50,000 years, have warp travel and even invisibility cloaks more advanced than any encountered by Federation science should have colonies or settlements in other star systems.
I wonder if the second part of the line "Some of you are the first of your species, some the last." was a reference to the Cheronian, or some other character(s) that they'll expand upon later.

