So I browse MMORPG.com quite a bit. One common thing you come across that I'm curious as to how you would fix/solve would be people who will mention without embarrassment that in the last month they averaged more than 4 hours everyday. So the question is do you make some sort of dynamic content for this group, add content you need to keep repeating, or just let them move onto the next game(probably complaining in some forum or another that the box didn't provide more than 200 hours of content).

I'm not into MMO's much, but I've logged over 300 hours of COD4 multi-player ;)

COD4 doesn't really have that much multi-player content, but it's balanced well enough to be a great competitive game. For example, I'm sure there's people who have sunk thousands of hours into Chess, which has had the same content for hundreds (thousands?) of years.

COD4 does hook the MMO-crowd with a sense of "achieving something" by initially restricting the abilities/weapons/equipment that you use. As you spend time in-game, and complete achievements/challenges, these things become unlocked.
Many of the unlockables are just cosmetic as well (e.g. new textures), but people seem to enjoy striving towards something.

I am not very into what the commercial MMORPG industry calls "dynamic content", because that usually just means it has a "content randomizer". Nothing says dull, meaningless play then recognizing that the dungeon you are in is nothing but shuffled tiles and encounters that have no bearing on the story or reason for existing.

I think the answer lies more in PvP-based activities. But not just PvP. I think a lot of MMORPGs are missing the boat with mixed PvP/PvE activities. For example, you could have an instanced dungeon that allows 2 teams of opposing-faction players in. These two teams have to deal with each other, and some mobs on their way to a boss. When they reach the boss, they, again, have to deal with each other, as well as trying to take out the boss. During the boss battle, there could be side-objectives to lock the opposing team out of the encounter so one side won't just wait until the boss is at 10% health to jump the other team and steal the kill. While it doesn't last forever (no content does), PvP elements in content will make it stay fresh much longer. Players come back with new strategies, different group make-ups, better gear, etc. There is also just something that makes a battle feel more epic when you know there are humans on the other end struggling for the same objective against you.

Going back years now when Ultima Online first released Champion Spawns and only placed them in the facet Felucca (which follows the rules anyone can attack anyone) they created something like this.

Anyone could try a champion spawn and grind through the spawned mobs which raised 4 tiers and each became more difficult. After the fourth tier was over a champion boss would spawn. At any point another person, team or guild could come through and try take over the spawn. Having to fight off other real players while still trying to keep a constant damage on the champion boss was challenging and fun. There were problems in the system but its still one of the best "raid" systems I've played.

I do believe basing more aspects of the game around PvP would work in the best interest of everyone. I’d aim to please PvE fans by giving them the supporting role. I'm a PvP fan though so my opinion might be biased ^^

I think something that could work is to create some sort of mechanism that allows them to play more casual. When you create a treadmill you basically just encourage burnout and the eating up of content at a very fast pace.

For example the player completes a quest and gets some land. They can use the land for a farm or a factory or something like that. In real time this land will collect action points that the player can spend upgrading that land.

Combine this with other traditional forms of MMORPG gameplay and an economic system that provides a large variety of goods to obtain.

The general idea here is that the player has insentive to keep their account active but they don't have to play 4 hours a night either.

Another key to this system is to get away from player base stratification. MMO players are much more likely to keep playing if they are playing with friends.