Even if these routes / rolling stock appear after the 'new' game it shouldn't be a problem. The new game will be totally separate from our current TS (or at least that's the impression) meaning that there is still a large userbase to sell to. If the new game follows a similar path to the original Railsimulator, then there will be a slow uptake from the current userbase as TSxxxx will be good enough for them, then once more rolling stock or "the killer route" (such as WCML N was for Railworks) then the uptake of the new TS will suddenly explode (maybe, possibly).
What I'm trying to say in a very roundabout way , is that TSxxxx will still be a good platform to release products on even when the new one goes live for perhaps up to a year after launch.