You say you don't want the level cap to increase because you don't like hunting down higher level gear, but the reason to continue playing if the cap is frozen is to keep looking for special gear?
What's the difference if the new "high-level" gear you're looking for is level 100 or level 110, once you've reached those caps? If you're questing in a new world with a new story line, what's the advantage to not gaining experience, not advancing levels, and just finding different level 100 gear than you had in the last world?
I get that at some point when you're in the last world currently available you hit the level cap and the last few quests offer no XP or level advancement, so it's not really a compelling argument to say people would have no reason to play without it. But I don't follow the logic of permanently freezing the level cap at 100. Perhaps a different explanation would help.
And we would continue to quest because.... ?? The level cap should continue to be raised otherwise there is really no point to continued time invested in the game.
10 bucks for 1 month membership is really cheap. Personally, I would keep playing and subscribing b/c there is no way I would stop playing forever since the time invested would worth nothing in the long run.