It's Robert Scoble who started this whole thing, with a FriendFeed post (is that like Twitter? I can't keep up) that reads: "Why did Google announce Chrome OS this week? Well, of course, Microsoft has a big announcement coming on Monday (I'm embargoed)."
Let the speculating begin. What's already more or less confirmed is that Microsoft will announce coming Monday that Windows 7 has gone "Release To Manufacturing". Now, is this a big enough an announcement to make a hubbub about? I'm not particularly sure. If we were to take Scoble at face value, it's somehow connected to Google's Chrome OS announcement, which opens up two other possibilities.
Some have pointed at Gazelle, the research project that we detailed yesterday. It could be that Microsoft is planning some sort of announcement (a product) around Gazelle next Monday, but seeing the experimental state of Gazelle, I highly doubt they will. They have been talking about Gazelle quite a bit, though.
Microsoft blogger Long Zheng did some serious digging around and putting-pieces-together, and he comes to the conclusion that the big announcement will be Office Web application. Not as exciting as something like Gazelle or maybe something even more exotic, but Zheng's analysis is thorough, so I'm inclined to follow his lead.
Maybe some of you have other ideas?