I wrote a Breakfast Topic recently concerning the somewhat ambivalent effect that Death Knights were having on the usual tanking shortage, but wasn't too surprised to see a lot of people (perhaps most) write in to note that the healer shortage on their realms was even worse. Leveling as a healer -- even with all the changes to spellpower and shared gear -- is an unattractive proposition for most, and a lot of people who healed at 70 want the chance to do something different. Past a certain point you'd give anything to be doing something that doesn't involve staring at a series of dropping health bars, and that doesn't lend itself to a large and willing population of healers cheerfully offering their services for 5-man use in LFG.
My main's a Druid and I PuG a lot, so I have the luxury of being able to observe which spec is the most wanted for 5-mans (at least on my realm). As soon as dual specs become available, I'm going to have a PvE tanking and PvE healing spec set up and ready to go -- and after that, I'm going to keep a little notebook and tally how many times I get asked by a group to heal, and how many times I'm asked to tank ("But what if someone wants you to DPS?" you ask. What is this "dee pee ess" you speak of, strange one?). With an increasing number of Death Knights reaching 80, I'm willing to bet that the demand for healers is going to be even greater than it is right now, and that increasing pressure is going to be exerted on hybrid tanks (i.e. Druids and Paladins) to maintain a healing spec and gear in order to ensure that groups get off the ground faster than they do right now. I could be wrong, but I'd also be lying if that wasn't the dominant trend back on Wrath's beta with respec costs at 1c and a ton of Death Knights at 80.