Exactly what I've been saying. Also, spot on about the "Back to My Mac" feature. I wrote about this in my iMac prediction post (the part about "Option B"). The only con is that you would require a high-speed internet connection, which isn't always available... especially on those long trips you speak of.
3G ie. HSDPA and HSUPA. Maybe? Europe/Asia it would work out well.
I guess it could go one of two ways. An ultraportable to do as you say. Which would be pretty neat.
OR
Something close to that Intel prototype. Again probably something I'd consider as it has different strengths.
If it's the latter I'd hazard an optomistic guess at the 1.8GHz 17w TDP Merom LV (L7700). Due out in September.