I only slightly mentioned this back on the podcast, I think, but there was a fairly interesting change that snuck in the patch notes on 2.4.2: lots of formerly main hand weapons have become one-hand weapons. There are a couple of theories poking around about why this could be -- dual wield is first and foremost, of course, as this change allows classes who dual wield, including Rogues and Enhancement Shammies, to have a little more choice as to what weapons they can use. Death Knights will also be able to dual wield in the expansion, and this will open things up for them a bit as well. And Blacksmithing weapons were apparently changed as well (in addition to losing their "unique" status), so Blacksmithers have a little more leeway, too.
But there is one thing that, according to Blizzard, will always keep weapons in one-hand status. Caster stats, according to both Drysc and Hortus, will mean that weapons will always stay one-hand. So feel free to do as much switching around as you want in terms of speed and melee damage, but there'll be no stacking of healing or spell damage bonuses (with Shamans or Death Knights).
Which isn't really a big loss -- it means that Blizzard has much more leeway in creating healing and spell damage weapons than they do while making melee weapons. But it does mean that if you want to play around with weapon combos, you have to go melee -- healers and casters get to choose one and stick with it.