Fortunately, the Young Justice FanDome panel did drop some more details about Season 4.
It should be interesting to see if episodes of Young Justice: Phantoms are noticeably different than Young Justice: Outsiders when it comes to the performances.
If the voice actors can’t get to a recording booth at a studio, they can just make their own recording booths at home!
That said, there is no saying when the show will return with Season 4 episodes, so there may be plenty of time for Greg Weisman and the rest of the production team to perfect the process from home.