Brace yourself, end of SteamGifts (and game-trading in general) incoming?

They have not. Although it's not entirely clear what limitation you are referring to.

At best it'll divide the population of this site into groups coinciding with Steam regions. But I suspect that the site will be solely for USA citizens.
It also means that if a game is unavailable in your region for whatever obscure contrived reason there will be no way you can get it.

It does not, not yet at least. So far the new region restriction method looks like an upgraded "onlyallowrunincountries" flag, the only difference being a new "reservation" created for South/Central America in addition to RU/CIS. This will only become a problem if a) more publishers start using it, and b) more regions are created to enforce region separation.