im sure its gonna be a ipod dock connector.

The only way to do this is using the proprietary dock connector, just like hundreds of home entertainment systems and portable stereo's do. Apple has enough market share so they don't care if they lock people with other devices out...

I believe the only true way to support all the devices is to run thin clients with USB support. This will come eventually, because I personally know people who are trying to get this tech on United aircraft.