Wouldn't be surprised if that was in their roadmap since they focus a lot on catering to "power users." That's why I grabbed one and am moving my BTC from my Ledger over to the Trezor.
One other cool thing about the coinjoin is it requires you to use Tor so although an external service is used to mix they don't know your IP.
Definitely would love to see Joinmarket integration connected to my own node in a future update for sure tho.