What's the Mission?

But what exactly can the X-37B do, and how will it be used?

X-37B Space Maneuver Vehicle (SMV) is a suborbital, fully recoverable Vehicle.Seems like test vehicle for larger one to come once the concept is proven.

Does the program signal a sea-change for how space activities will be executed?

There is little doubt that the project is precursor to Millitary Space plane to weaponize space.

What do you think the mission is?

For recon or even deliver temprory small satellite for tactitical missions. Apart from obvious millitary applications, the vehicle has a potential dual technologies for civilian application for reparining satelite with extending arms or recovering space debris etc.

Yo, try to act at least semi intelligent, if the USAF wanted to "weaponize space" there are far most cost effective ways to go about it than developing a suborbital, fully recoverable vehicle". The fact that it is a fully recoverable vehicle points to a need to retrieve something. Data? Nah, they would just electronically transmit that, has to be hardware they want to recover. Maybe some old used up satellite? Russian? Chinese? US?