In my opinion, it's not as bad as some people make it out to be. The beta's actually quite fun to play through. As for the direction the game's headed...
There's a lot of people complaining it's more of the same. On the other hand, Blizzard would get just as much criticism if they did a massive overhaul of their core mechanics, changing the game 'too much' for some people.
Difficulty... I think they're doing a fairly good job. As it stands now, they release new content that's decent, adding easy and hard modes respectively, and make that content available to more people over time. I'm sure there's a few hardcore raiders around that will disagree with this, but imagine how frustrating it is for someone to invest a very large amount of time in a game, only to have the game tell you you can't see the end because you're not good enough.
If Blizzard keeps going the way it has now, there will be several layers of difficulty to choose from, and if Dragon Soul is an example, you can yourself choose to play it as it was before nerfs. With the addition of Challenge Modes for heroics (Which is basically a 'no outgearing this mode, show your skillz' setting), I think it'll hold something for everyone.
Lore... Granted, going downhill fast. We're at the end of Cata and we still don't know what ended up happening to Neptulon, as one example. For another - and I'm not happy with Blizzard for this one - is that the leader of the Infinite Dragonflight, one of the game's most major threats in BC and Wrath, was offhandedly killed in some random heroic. Then, Blizzard has already received tons of criticism on the topic. We'll see what they'll end up doing with it, but I'm not holding my breath.
Optional stuff... Yes, by this I mean the Pokémo- err, pet battle system. I'm not sure if I'll be using it myself, but I like the addition. It's something different to do for the people wanting to waste time with something other than standing in capitol cities, and it's entirely optional. As long as it's not forced on players who want to stick to the core of the game... Why not.
Overall, I think this won't be WoW's last expansion. There will be plenty of people (myself including, despite some flaws) that will continue to play regardless of the new additions being made to the game. There will always be people that agree as well as disagree when new stuff's implemented, and WoW's continued existence is proof it can dish out enough good content to overlook the bad for most.