All gone by summer 2020 is their latest statement.
Training is their current excuse for the delay: "“They are in Yorkshire for one simple reason – that is that our train crew here can drive them now, can operate them now. If we introduced them elsewhere where they don’t operate them now, we would introduce a training need that could not be coped with."
Drivers need to be competent on the specific type of train. This seems especially obvious for a driver who has spent the last decade driving Pacers and might now be given a Class 195 DMU. The handling characteristics are pretty difficult, it's not even like it was a small upgrade - as observed so many times a Pacer is basically a railbus.
If anything the anomaly is that we aren't expected to retrain on the roads. I am old enough to be "grandfathered" into the UK's old regime where a single pass, as a teenager, in a small hatchback, qualifies me for like 50 years to drive a 5 tonne truck even with a trailer. I've never driven anything with a trailer, no evidence I'd be safe doing it but hey, the rules used to be lax so...
The use of "excuse" was referencing the fact that these trains didn't just up from no where, that training on new trains isn't an unexpected thing for a train company to need to do.
It's like saying a product in a supermarket is delayed "because it needs to be put on the shelf"
https://www.youtube.com/watch?v=NScxhRR3LyY