If higher points would have some kind of relevance (like if you could spend them) then I would agree. In the current system however only your total percentage "matters" if you're an Achievement hunter and in this sense you'll "lose" progress anyway, because the expansion will add tons of new Achievements. It's easier to compare two people by points for sure, but since everyone will lose some, if you're ahead now you'll be most likely ahead even after the expansion. Again, I don't see what the fuss is about.
As for Feats of Strength, I think WoW is a perfectly valid precedent and there Feats never gave you Achievement points, counted in your total percentage, or mattered in any way.
If someone wants to have every Feat in the game, then they should finish every Achievement that's linked to the old difficulties before the expansion comes out, which shouldn't be that hard to do. People can check out on the PTR what will go away.
