No, they said that all cars from GT4 would be in, which they appear to be.
My suspicion is that PD have fundamentally changed the way the underlying framework of a track is either modelled or processed from GT4/GTPSP, presumably in the pursuit of efficiency to achieve their goals of 60fps, 16 cars etc. This would mean that bringing tracks from GT4 wouldn't simply be a case of re-making textures, but would effectively involve re-modelling from scratch. It may even be that there have been two iterations of this modelling improvement, which might explain why some tracks can have weather and others can't - the others are possibly not 'streamlined' enough.
As for the prospect of DLC, someone commented that there won't be time to produce DLC as there hasn't been time to include those tracks in the main product. This is a fallacy - while it's unrealistic to believe that new tracks will appear every month or two it is reasonable to believe that they might continue to produce tracks periodically over the next few years (as they'll hopefully be needed for GT6), and assuming a lifetime of three years for GT5 they may be able to provide half a dozen new tracks.
And yes, I'm afraid I believe that this list is what we're getting, and that there is nothing more to be revealed.