Yeah, the fact that they already have a timetable that far in the future makes me pretty sure that it's a legal hurdle and not a technical one that's in the way of a downloadable app. Since Netflix signed an exclusivity deal with Microsoft to have streaming movies as a console feature, this is probably just a legal loophole in the language. And I wouldn't be surprised if Microsoft go after them to block it.

Personally, I'm not sure which platform I'd rather use, since they both have their limitations, but fortunately I can just use Netflix on my Mac HTPC with Plex.