The focus on the routes in the Pioneer edition might give us a clue to the initial focus for TSW - i.e. modern, modern and modern. I'm going to stick my neck out (as I have NO inside information on TSW) but as DTG's focus for a long time has clearly been purely on modern railways I suspect that if you like anything that happened before 2000 then it's going to be quite some before TSW can scratch your itch for train simming.
Remember we've been here before when Rail Simulator came out. Lots of people stuck with MSTS due to the enormous amount of available routes and stock and it took quite some time before the RS world started to fill up. Now admittedly this time DTG is over 100 people strong, rather than 6, and there are quite a few 3rd party developers so it will probably be quicker than before but clearly the level of detail required is going to have an effect as well.
But colour me excited! The prospect of such detail, the promised base systems that can hopefully deliver the realism we've craved for years, multi-player, a dispatcher that's not a total chump! The future is bright indeed.
I remember feeling like this when Railworks came out (before that the lack of steam engine chuffing left me a bit cold!) and I took a look at the scripting and blueprint system and thought - hey, we can do good stuff with this. 7 years later and developers are still pushing the envelope of what can be done in the way of realism (advanced locos) and effects (such as the TPO coming with the GWR Saint - it's soon, I promise!).
However it's going to be a process as people migrate to TSW, likely running both sims for some time until the locos and era they want to re-create are available in TSW.
From a company point of view, we still have many locos we want to build for the existing TS and hope that people will continue to buy and enjoy them. We've already set out some time to look into modelling in UE later this year (in fact we had a little dabble last winter) but I expect TS will still remain our primary focus for the immediate future unless DTG come up with a surprise steam era route. Somehow I'm not sure any of our locos would look right chuffing up Sand Patch Grade
