Even so, I have to wonder if the "generally satisfied" attitude of the PoE community today will bias said community to hostility toward a sequel, if such a thing ever happens. I'd be a lot more interested to see a future PoE 2 forum, since we're actually talking about Guild Wars 2, here.
They have done some major changes. Bigger than GW2 imho. The game is fundamentely different from what it used to be in the beta. And the only "overwhelming" negativity I have noticed is in the racing forums and it's justified imho.
To your second paragraph: Wait what? You started out with "any MMO"... I guess a lot of them weren't sequels. I also refuse to believe that the grumpy GW1 players are still the majority of complainers/people that are dissatisfied with the game/devs.