I think one issue with the Gold saucer activities is they are overly complex (LoV) and/or somewhat unrewarding. With so much MGP earnable by just doing the daily cactpot every day there isn't really much reason to look to other sources of MGP, particularly when they feel clunky or overly confusing.

As a general rule I think alternate content to raiding or even dungeons would be nice to see. Exactly what though is hard to consider since its hard to know what the game can actually manage. Perhaps more developed FATE system could hold potential. A lot of people enjoyed the Darkscale chain for a while.

Of course, like Gold Saucer, it's reward to effort ran out pretty quick but it was definitely fun. I would like the Gold Saucer to feel more like a themepark than something I need to spend time reading a manual to enjoy. I don't fundamentally have an issue with chocobo breeding but if our just wanting to do some races, most players are going to be more interested in skill in a race over breeding I suspect. The reward doesn't seem to match the investment needed. Likewise LoV. The main turnoff for me is there was just too much variety in the minions to the point that I wasn't really sure what to use for what. Gold Saucer doesn't feel rewarding enough to justify theory crafting. Plus both forms of content are hard to do in sizable groups and once you have enough MGP to buy what your after there is very little reason to go back and do it again.

PvP I think they are making good improvements on, though it still has a way to go, particularly with the ranking system. I tend to be a casual PvPer. My main reason for stoping doing Frontlines was when I capped on Wolf Marks and didn't have anything new to spend them on. Adding some form of consumable or alternate currency sink would be useful. Hell, even adding sets more regularly.

I'll be curious what they have planned in 4.0. Deep Dungeon was a winner for me and I am looking forward to future ones. Diadem 2.0 we will see about in a few weeks. Beyond that, a spin on instanced content could be interesting that break the Mold. Maybe a version of Hamlet defence. After all we are in a warzone. Defending a Eorzean Alliance outpost from waves of Garlean attackers could be interesting, particularly if you mix it up by adding things like Cannons to the defence.