There are a lot of professional musicians who play live with Gigastudio, a Windows based sampler. That's a pretty demanding program, but if a good computer is only loaded with that software and nothing more, it is no problem. I think the same will be true for an arranger synth. But I think that arranger players will want dedicated buttons on a console to control style variations and what not.

I think some developments on the horizon will be:

1. More and more realistic voices
2. Superior style morphing
3. Improved ability to create styles out of midis
4. Music Finder databases that can call up style, tempo, and any other desired parameter
5. More voice editing capabilities
6. Pitch correction on the vocals
7. More realistic vocalizers
8. Human voice modeling so that someone with a mediocre voice can sound more like Frank Sinatra. I'm not happy about this one.
9. Ribbon controllers to create arpeggiations
10. As everything becomes more miniaturized, they might create an accordian arranger that has everything on it.
11. Each year, the top arrangers have more and more styles. Ten years from now, you might be able to choose between 10-15 Mexican styles, a dozen Celtic styles, and many Arabic and Indian styles. The top arrangers might have 600 or more styles instead of 250.

These are some thoughts

Beakybird