I just got an email from my friend Joe Thompson (from Eagle Colorado), who is at Camp II on the Nepali side of Everest. He is with an American expedition and has his dog Denali with them.
They arrived in Nepal on March 20 and are currently at Camp I and should be headed towards Camp II today. As far as is known, Denali is the first dog ever to attempt the Everest climb. Dogs have made it to Camp I before, but not beyond. They expect that the summit attempt will take place sometime mid to late May, but that depends on weather and conditions.
Here is a picture of me with Denali (the one on the right) during our climb in Colorado during a blizzard: