Sometimes the title of the post says it all. Is your raid leader requiring dual specs? If not, is he or she planning to?
While I've retired from my raid leading responsibilities, back in the day I probably would have "asked nicely" a few people to pickup dual specs, even going as far to have the guild pay for it. Of course the people that I asked would have likely been doing it on their own anyways. For instance I had an awesome Paladin tank who did just as good as DPS.
Right now the primary situation where dual specs are useful revolve around 10-man groups. Some fights are quite healing intensive and less of a DPS race. Those would benefit from having a hybrid switch from DPS to healing. An elemental shaman switching over to resto to heal the raid can make a major difference.
So how about it, is your raid leader making you dual spec?