For handheld gaming I see/use three distinct use patterns:
#1 in the wild, away from any LAN/WAN or (generally) external power sources
#2 not-so-wild, online gaming with (or without) external power sources
#3 similar to #2 above but streaming FROM local or online sources
Obviously MS will want to offer products that are tied to their subscriptions however being able to stream from an existing Xbox (or PC) in another room or having a group of handheld players "team up" and play together in the same room (or not!) would likely require MS online services and $$$.
I'll go out on a limb here and say MS is going to use an "X Elite" chip for their handheld, snubbing both Intel & AMD in the process. :)