Of course, it is easy. When you're already assuming something like RSS feeds for app updates exists, don't you think it's possible to have an application download them once a week and update all apps automatically? For an end-user, there's no difference to APT.

Also, you seem to misunderstand the point. To have a third kind of distribution -- "stable foundation and recent apps" -- doesn't affect your choice of distribution, at all. When you're satisfied with Gentoo, you simply continue using it.