The timing of Google’s announcement of Chrome OS was curious. I don’t mean the fact that Google moved up the post on it by a day when some details leaked out, I mean the fact that they were announcing it on some seemingly random date in July, well before anything is actually ready to show off. Now, we likely know why.

On Monday, Microsoft is set to unveil its plans to counter the attack Google previously had launched on it with Google Docs. Yes, Microsoft Office is going to the cloud. This is something which we all knew was eventually coming, and there is already some limited functionality, but the full details will pour out Monday at Microsoft’s Worldwide Partner Conference in New Orleans. You can expect the new version of Office, that syncs with the cloud, and the ability to use it in the cloud without any software as well.

Almost immediately following the Chrome OS announcement, Robert Scoble took to his favorite home on the web, FriendFeed, to have one of his, I-know-something-you-don’t-know “discussions.” During the course of those “discussions,” Scoble gave dropped quite a few hints about what Microsoft planned to announce on Monday, including “Diego, no, it’s one of Microsoft’s primary businesses. Did you know Microsoft has 14 billion dollar businesses?” Guess what that is? Microsoft Office.

It doesn’t take a genius to put two and two together. And several bloggers already have. And it was especially easy after Scoble ruled out the new browser project Microsoft has code-named “Gazelle.” Scoble also noted that what Microsoft was showing off would run in browsers beyond just IE.

So yes, it’s Office Web that was first talked about at PDC last year.

And it’s possible that Microsoft could unveil that this new web-based Office will reside and the great domain, office.com. That site is clearly going through a transition to new ownership right now, and that would make a lot of sense.

Office is obviously the 900-pound gorilla that Google is attempting to slay with Google Docs, but a 900-pound gorilla with a matching web offering will be a lot tougher. And that’s likely why Google wanted to get its own uppercut in first this week. And it’s a strong one. But now Microsoft is going to have to come up with some answers to how it can counter Chrome OS, rather than focus on talking about the new Office.