Technically, I could form my own caliphate as well. Who's on board?
Yeah, the Caliphate under the Ottoman's was pretty much symbolic, an artifact of history that mainly still existed to boost their credibility. Initially, it's only purpose was to give them causa bellum against Muslim nations, allowing them to DoW without a stability stab or infamy penalty. Any attempt to re-establish a caliphate would probably be by a fundamentalist government without such moderate leanings. But I've seen "caliphate" thrown around a great deal without any sort of proof that it's actually happening or apparent knowledge by the arguer of what the hell they're talking about. Just some vague conspiracy theory. The newest "evidence" thrown out, that being Libya's conversion from Sharia law to Sharia law, is the most laughable yet.
Interestingly, back in the 70's there was an attempt to unite Libya, Egypt, and Syria (and, at one point, Sudan) into a single state. It actually passed referendums in the countries, but wasn't ever implemented. There might be some pan-arabian spirit left in the air. However, pan-arabism has generally been secular, not something pushed by fundamentalists.