Originally Posted by
Lemuria
Let me reverse that question by asking you which MMO's you've played which have? Seriously, I've never heard of a game which raises the level cap past it's current level then decides not to allow people in the earlier areas to level up. Experience is experience, no matter where it's earned. There's literally no reason why the level 50 dungeons shouldn't provide experience other than out of spite for not buying the expansion.
Now, if the entire level 60 had been gated off through an Ishgard quest, maybe it would be different. Incidentally, FFXI didn't gate level rises behind expansions either. Once the level cap was raised, the quest was available to anyone, expansion or not. The expansions added plenty of nice areas to get XP faster, sure, but you could still earn XP at the maximum level in earlier zones.