If this device is to succeed in Europe/UK, it will require 3G and MMS messaging.
Features like iChat will more than likely be added, plus maybe flash, ringtones and games would be obvious software updates like youtube on appleTV.
I don't get the need for MMS messaging. A simple e-mail solves that. And if AT&T were smart, it would just fowarded all incoming MMS messages to your e-mail address.
I am sure Apple thought of this.
Problem solved.