The Wersi OAS and Lionstracs Mediastation both support WAV/MP3/MP4/MIDI/Video and much more.

It appears most of the features people are referring to, the Wersi and Lionstracs already have! Perhaps one should pony up more money and buy one of these instruments instead of the usual suspects (Yamaha, Korg, Roland).

The Wersi OAS 7 even has Open Art Arranger software which allows direct playback of Yamaha style files with no conversion. The Wersi also includes the Tyros II sound set so you can sound exactly like a Tyros II if you want. I'm not really sure why you'd want to sound like a Tyros if you own a Wersi, the Wersi sounds are far superior in my opinion, but they are there if you want them. I believe the Mediastation also has a Tyros II sound set as well.

The other advantage of these instruments is the ability to load nearly any sample you want (AKAI, GIGA, Kontakt, etc.) as well as nearly any Plug In or VST you want to use. The sound possibilities are nearly infinite.

The future of what arrangers will be has been around for quite some time... The Wersi OAS has been around since 1999/2000. In time all new keyboards and arrangers will be open ended, it's called progress. No matter how hard Yamaha, Korg, and Roland try to keep selling embedded systems, eventually they'll have to follow Wersi and Lionstracs lead and change to open architecture. Korg's Oasys was a good start but Korg could learn a lot from Wersi.