In the recent Twitter developer chat one of the questions asked was whether crowd control would make a comeback in Cataclysm, and the answer was "an emphatic yes". My first reaction to this was: "Nice!" My second was: "Erm, how?"
Spinks touched on the subject of crowd control in a recent post of hers as well, and on how people tend to have a bit of a love/hate relationship with it. It's fun to be able to use different abilities for a change, but it's not necessarily fun to have to wait around while other people go through their own special moves, or even worse, to have to limit yourself so they can do better (for example by leaving a high-damage AoE attack out of your rotation so you don't break the shackle).
In casual group content you're likely to gravitate towards working in whichever way is fastest and most efficient, even if that leaves out certain bits that you personally find fun. It's human nature. Thus, if you want people to use crowd control, you have to make sure it's part of the most efficient way of handling things, or in other words, you have to ensure that not using it is so inefficient that it gets you killed.
In BC heroics we had to use crowd control mainly for two reasons: Firstly because tanks simply didn't have the tools to reliably hold aggro on four or more mobs at once, and secondly because some mobs did so much damage (whether on the tank himself or with abilities that targetted the rest of the group) that trying to tank them all at once - even if you could theoretically hold aggro - would result in death because the healer couldn't keep up.
Both of these factors pretty much disappeared completely in WOTLK instances. Tanks got AoE threat abilities that applied to an unlimited amount of targets, so they tanked unlimited amounts of targets. Like, duh. (One of my very first posts was about this subject as well.) And the mobs in Northrend heroics didn't really hit that hard anymore either, not even back when we were all in blues.
I still remember the very first time I set foot into a BC heroic at seventy. It was Slave Pens, by many considered the easiest one of the lot. Nonetheless we wiped about three times in the first room alone, as our tank just got turned into paste over and over again. Eventually I figured out that I had to wind up my biggest heal before the pull and time it so that it would land exactly at the moment when the mobs started to hit the tank, and then I had to keep spamming that same heal non-stop until most or all of the mobs were dead. I never encountered anything even remotely as unforgiving as that in WOTLK.
This is how we got into the "just AoE it all down" mindset that is so prevalent today. But can we actually go back to the way things way before? I actually don't think we can.
As far as tank threat goes, the problem with being able to generate threat on an unlimited amount of targets is that it's... well, unlimited. You can't make a pull of "unlimited plus one" mobs and then say: "Ha-ha, now you'll have to crowd control one!" No matter how many mobs you throw at a tank, his ability to keep their attention will be the same whether he's up against four or fourteen opponents. Thus the only way to make lack of tank threat a reason for crowd control again would be to severely hit all tanks with the nerfbat. The devs have actually made a comment or two about wanting to nerf AoE tanking a little bit, but to be honest I have a hard time imagining that they'll actually go through with it, not when there still aren't enough tanks to go around for most groups, despite of several tank specs having been buffed to hell and back. I don't think anyone wants to have crowd control back so badly that they'd rather wait even longer for a tank for their pug group.
Making heroic trash hit harder again would be an option of course, except that that would go completely against Blizzard's plans for making healing less frantically spammy in Cataclysm, because spam is what you have to do if a mob can hit your tank for half his health or more. Yet if the mobs don't hit that hard, there's no reason for your tank not to hold them all at once, and thus again no reason to use crowd control.
The only alternative I could personally see would be to make sure that a lot of trash mobs have extremely disruptive non-damaging abilities on short cooldowns. Imagine a pull of three mobs who all try to cast mind-control on someone in the party every five seconds. Or mass-fear constantly, or keep spamming heals on each other. The abilities would have to be fairly powerful and highly stacked to be really disruptive though, considering that a lot of mobs in WOTLK instances stun, heal and so on as well, but still don't cause considerable issues.
Then again, maybe the creative people at Blizzard have a completely different solution in mind. No matter how they go about it however, it will have to be quite punishing to not use crowd control, or else people just won't. The new ICC five-mans for example struck me as an example of mechanics that tried to "encourage" crowd control but pretty much failed utterly. Forge of Souls for example is chock-full of annoying, high-damage-dealing casters who are so far spread out that it's hard to AoE them properly, an invitation to just sheep at least one mob if I ever saw one. But how many people actually do it? In all the runs I've done of the place I think I had a mage sheep something once and a hunter who used a freezing trap once or twice and that was it. Or take the two pulls at the bottom of the ramp in Pit of Saron. Again, casters that are quite spread out and deal massive damage, yet most groups would still rather wipe three times trying to brute-force their way through than use crowd control. I'll forever remember the one time a death knight tank asked me to trap one of those casters while I was on my hunter, because it was just such a rare event.
If they know it can be done without CC, people will try to do it that way. Which kind of makes you wonder how many players really want it back anyway.