I'm sure that the District will ask the full circuit court to rule ( en banc). Probably we loose on that. Then to try again for certori in the Supreme Court.
If so, hopefully we get a hearing. And if so, what position will the Trump Justice department take?
I don't think they will appeal this loss for the reason you gave: they'd win en banc and then we'd have the right to seek cert by SCOTUS in 1 - 2 years. Many think Kennedy will retire next June. RBG might "go" at any time. Breyer is no spring chicken (late 70s). Once the DC asks for en banc appeal, the process is out of their hands and they may end up defending their May Issue law before a SCOTUS packed with pro-2nd A Trump appointees. If they lose there, the 8 remaining May Issue states (yellow in the map below) will either have to go Shall Issue or allow Open Carry (incl D.C. and NYC). Since OC is banned in CA, that means Shall Issue for all 33,000,000 of us, that's especially important for the ~19,000,000 who live in the major urban counties that rarely issue CCWs.
Instead, I think the antis will cut their loses, lick their wounds and hope a Dem wins in 2020 (or antis at least take back the Senate in 2018).
We should know whether DC chooses to ask for en banc appeal or SCOTUS for cert instead or decides to not to appeal by the end of August.