Google sends out invitations for a mysterious mobile-related event
It can also be something policy related like the recent net neutrality agreement with Verizon. On the hardware front - tomorrow is the retail launch day of the Motorola DROID 2, and Samsung's tablet with Android 2.2 has to be announced soon as well.
It can be any of those things, or something totally unrelated, but we hold hopes in our hearts that it will be more goodies coming Android way. Your guess is as good as ours, but thankfully it will be known very soon.