I don't think IT is really any different to any other industry here, despite the pace of change. If you buy in skills, the company providing those skills should provide a service that is "of merchantable quality".
However, that doesn't mean they should necessarily be walking encyclopaedias in their given subject. It means they should be capable of doing the job you're asking, and if that means a bit of research, so be it. I wouldn't care if a builder, uncertain about building regulations in an unusual circumstance, did a bit of research to find out what was necessary - I'd be far less happy if they didn't!
What I do believe to be fundamental to the requirements of a consultant, though, is that they can and do ask, correctly interpret, then deliver the solution for the question, "what are you trying to achieve?". That, to me, is the value-add that you pay for. So many consultants only listen to what the customer says they want (and only half listen at that), and try delivering that without questioning, verifying, sanity-checking or burrowing down to real requirements. The technical skills are, to my mind, irrelevant if that first important step hasn't been done properly. Following my earlier analogy, "I know the customer said they want their house built on sand, but it doesn't matter how good a bricklayer you are, it won't work well for long."
Semper in excretia, sumus solum profundum variat