I usually go after some kind of goals when I'm playing WOW. I just do so with the understanding that I might not complete them because I may burn out for a while, or I may find something else to do, etc. My friends and I had all kinds of plans for WotLK, then we all stopped playing WOW for various reasons.

I don't see a problem with preparing for the next expansion. Like others have said, I'll probably fall short of my goals. In my case it's because I'm not playing as much right now, and when I do it's unfocused (PL some toons, quest on another team, run a character solo, etc). But I do have some goals and when I find time I work towards them.