I really doubt they got pulled, do you realize how much work goes into each ad and how long ago they were probably made. If they are moving onto something else then that was decided way way way before people saw these ones..
I'll wait and see what happens and see if its any good vs analysing thin air..
The New York Times reports that there will be ads with Bill Gates with other celebrities, and that this is just the end of the celebrity ads which featue Seinfeld. Valleywag
is assuming because Microsoft called up news sources and notified them about how their campaign was moving into a new phase, that means they cancelled whatever they had and moved to th e new phase early.