I still haven't heard back from my rep at Shape Services, but I do think I know why a multi-protocol IM client is so long in coming. Currently, WP7 doesn't support independent sockets. What that means is that you can't just connect to ports and services. WP7 supports HTTP and HTTPS connections right now. Until we get socket support, we can't connect to the actual IM servers. We need to connect to a proxy server first.
The rest of the story is that Microsoft is, according to reports from various blogs, releasing the API during the first round of updates, so possibly in January, but more likely in February. This, of course, won’t be confirmed until we actually see the update, or a beta of it. I doubt someone will be building a web IM proxy to support WP7. Most likely, they will wait until the socket API is released. I don’t think we should give up hope, though. I know that there are several web based IM services that would work as a back end. Meebo, for example…
Anyway, that is what I am thinking right now. If I hear anything from my contacts, I will let y’all know!