This is the situation I'm in, and I suspect it's one that a lot of other hybrid players would recognize; I play restoration in most guild 25-man and 10-man raids, but I tank just about everything else. On easier content, or on nights when we have too many healers show up, it's not unusual for a few people to haul out their DPS sets and go DPS for the evening.
As such, hybrid players (and particularly hybrids who have dual-specced into a role requiring a completely different set of gear) have an interest in keeping their offspec set up to date, and the best way to do this has typically been through 10-man raids where there's not much gear competition. I got 3 Sanctified feral pieces from heroic 10-man ICC, and I'm still using a few ToGC-10 pieces to tank as well. When you only have 10 players in a raid, the number of players angling for a given piece is necessarily small, and items go to offspec quickly.
25-man raids couldn't be more different. For a specific example, I'm in line behind our feral, three rogues, fury warrior, two hunters, and possibly even two retribution paladins (!!!) for the Frostbitten Fur Boots off heroic Marrowgar-25 (yes, the number of people salivating over melee leather in Icecrown is amazingly annoying). Realistically, I'm not going to see this piece until the end of the summer or possibly even the beginning of autumn if the boots drop at their usual rate.
The situation's made worse when your guild makes the leap from normal to heroic, because the line just restarts. Anybody who wanted Toskk's Maximized Wristguards, for example, is almost certainly going to want their heroic version. So, rather than being 2nd in line for the next normal drop, I go back to being 6th in line for the heroic one.
As a result, the prospect of losing 10-man raids as an option to gear offspecs is a little scary, and I wonder if the raiding split is going to have an impact on the offspec that hybrids choose to play. Without the ability to build a bear set through 10-man raids, I'm really tempted to axe the resto/bear dual-spec and go bear/cat or resto/moonkin so that both sets share as much gear as possible. I don't think I'm the only hybrid player thinking about this.
An additional point for consideration: Is competition for melee leather finally going to die due to mastery bonuses encouraging mail and plate classes to stick to their armor, or is this just wishful thinking?
World of Warcraft: Cataclysm will destroy Azeroth as we know it. Nothing will be the same. In WoW.com's Guide to Cataclysm you can find out everything you need to know about WoW's third expansion. From Goblins and Worgens to Mastery and Guild changes, it's all there for your cataclysmic enjoyment.