In the final part of the episode, where they make anticipations about the next ep I heard Goku saying that Black Goku is even stronger than him.. lol
I wonder if Bills is going to do something at this point
Oh, someone said he couldn't transform anymore.
What we (or at least I) were saying, were just theories about Trunks not going SSJ against black Goku. Someone said he didn't go SSJ because he knew he had no chances to win against him and because he was just being smart and keeping is Ki to 0, and some said he wasn't going SSJ because of the lack of food and so lack of energy.
In this episode he fought black Goku in SSJ form, so yes he can still transform, though he's still low on energy