I've spoken to Oleg, there will be future builds in the Store that use FP10.1.
This is Fennec 10.02, there are the nightly, aurora, & beta builds still coming through.
Still getting clarification on what the plans are for the Gecko + Qt/SwipeUX builds.*
And whether they will also be eligible for FP10.1, doubtful....

*i.e. truly native & better suited the UX, probably more snappy too.