Chas... what I envision as to the future of arrangers, all of that is background technology. In other words, you don't change one iota what you are playing now... chords in the LH, comps and solos in the right. But what I see already starting to happen with software libraries like VSL (rule based sample switching), I can see happening to arranger's chord recognition and variation choice.

All that extra stuff goes on in the background, well away from the player's consciousness, just like what is happening with chord variations now. It will hopefully just be a LOT more sophisticated than it is now, with regard to chord analysis and variation generation.

I am looking for MUSICAL improvements in arrangers, not SONIC ones.

Half time and double time buttons... Intelligent 'swing' options, to swing 'straight' styles and vice versa.... There are many things we could all use on a day to day basis that are not yet available. The return (of course!) of the Chord Sequencer, with even more interactive options... Live audio 'loopers' for recording vocal backups or acoustic performances to be integrated with the arranger.

I don't believe the bottom of the barrel has even been reached, yet alone scraped!