1. Wait until the final version is released as you may find the Wave Rom is for the normal voices and sounds, with the loops having there own dedicated space.
2. You are assuming that all the new voices etc are samples, whereas they maybe synthesis or sound modelled, which takes up minimum Memory but requires a fast sound processing system. (This is the way Wersi have gone with OAS 7 for most of its new voices, although samples are still used to maintain compatibility with previous generations)
3. On the SD 1 you could load in Drum Loops to make up new styles, therefore it is probably the same with the Audia, but just expanded.
4. Technology is moving on at a fast rate, and if you look around, a lot of the manufactures of both software and hardware are starting to move towards the Sound Modelling route. (Yamaha SA voices use basic sound modelling techniques to improve there sampled voices)
Whatever the truth, the future for music keyboards is really exciting. (And yes I will probably still be playing my Abacus 10 years from now, but the sound system and software will be so far advanced I would not even try to imagine what will be available)
Enjoy whatever you play

Bill