No idea of an exact time frame unfortunately, but the likes of 4590, 4595, 4622 and 4632 had received a new MOT during the Autumn months, so if no failures occur hopefully they’ll be given a few months on top of the others I’ve stated below.
The electrics will transfer some E400’s over from Wolverhampton to replace the Tridents at Walsall is my understanding, and I don’t think that’s far away now, some have already been moved to Walsall like 4855/56/57. There could be more than this which I’ve missed.
Tridents likely to be withdrawn next from MOT expiry would be 4594 at the end of the month, then 4621 in March and 4612 in April, with those being the latest dates. Failures could also change this (as stated they won’t be repaired now)
Information isn’t provided for 4599, 4606 and 4610 so those are a question mark…