"Plan" posts are all well and good, but anyone that's been around MMO's long enough knows that the future is never a definitive thing. There can only be speculation and that's where the problems always arise. We know there's things you can't divulge and are subject to change, so anything long-term is going to be intentionally vague.
How about just simple Monthly State of the Game posts? "We are currently working on <insert things you can give info on", "We are looking for feedback on <insert things that are driving the community crazy>," "We are looking into <things that you know or think might need to be adjusted." Throw in some community things, some personal things around the office...
These types of posts are useful for a variety of reasons. It keeps the community in the loop, which lets face it, just wants to feel like they know the direction the game is going at all times. The posts are a compass. If they feel included, even if the biggest details are kept quiet, they'll be ok. It's the not hearing anything at all that drives them crazy. A monthly breakdown also helps you out. It takes away the big, looming expanse of future things and forces you to focus on the last 4 weeks. It's the here and now that matters the community and while we know you're human too, sometimes we need developers to talk to us like they realize it.
I just started playing, so I'm not accusing anyone of not listening to the community. This is something that all game companies tend to not comprehend completely. It's obvious you listen, and something just saying you're listening is enough to quell the frustrations. And from some of the recent posts, I think you've realized that. WOW used to do state of the game posts... They were just carrots. Take a look at Funcom and TSW. Their monthly director posts are not full of details or secrets. It's just a personal letter with just enough to give you a glimpse. And it keeps the community satisfied. Then when you do go into more details on features and things that are coming, you've not only satisfied, now you've gone the extra step. I think the gaming introverts that most of us are forget that the community management side of things are almost identical to a marketing team in the extrovert world. It's not what you say, it's how you present it. Don't worry about leaving out details and disappointing people. Just having regular updates of any kind are what's needed.