The only thing I've heard is the new UE4 engine edition is still in development alongside the current TSxx engine, with the current one still being supported once the UE4 version releases.
I don't imagine there'll be a UE4 release this year. UE has quite the learning curve and it'll take some time to create new assets etc for it. I think DTG will just continue to support TS16 until the UE4 version drops and they'll go for a simultaneous release.
On a side note, I hope DTG utilize this amazing concept known as "optimization" for the new engine, something which has alluded them since the Railworks days.