Yeah,
Because it is much better to release an expansion once every two years that most raid guilds finish the release content in under a month.
It really sucks to play EQ2 where hardcore raid guilds are still trying to complete content included at the launch of the expansion six months later and most will still be trying to finish it when the next launches.
It sucks not having all the content on farm status a month after launch, and having to look forward to a lot of new content once per year.

Gnova wins that one I think.

Underfoot sounds like it might be an expansion, as you mentioned. But don't forget about the past evidence of SoE hiring for a "flagship project". Underfoot could be a codename or something (if that's even possible, fell free to tell me why it is or isn't possible) for a new EQ game all together. Which I'd welcome of course.

Well "Underfoot" very much ties in with EverQuest lore as the home of Brell, creator god of the Halflings, Dwarves, Gnomes, Gnolls & several other races.

Access to the "Plane of Underfoot" was mentioned several times in the Lore connected to "The Hole".

Sounds interesting, I quit EQ because SoD was such a pile of crap expansion (as far as I am concerned) , I'd be tempted to check out an Underfoot themed expansion but it would sure as hell need more going for it than SoD had, perhaps with Free Realms doing so incredibly well SoE can invest a little in (or not suck out of) EQ this year & do something decent.