Once again, I'm late, but it looks like the Eclipse Foundation has extended an invitation to Microsoft to join its efforts. I guess they think their new directions on web services and SOAs might be of interest to Microsoft, since they're the market leader, right now.
Personally, I don't expect Microsoft to support this. First off, Eclipse has a long way to go to compete with Visual Studio. Secondly, do you seriously think Microsoft will support development for a product on a platform that it is a direct competitor for? Would anybody? I know I wouldn't. I mean, if there was some sort of integration that .NET developers, or the .NET platform might get out of it, then that's one thing. Otherwise, it just doesn't make sense.
One thing being looked at is whether or not to add a platform-neutral layer to its Eclipse Web Tools project. I don't know if this is in addition to a Java approach or not, however. I would hope that this wouldn't be a duplicate. That would be more code to update, which just doesn't make much sense. I'm sure each of you have tried to maintain two similar code bits (small or large) at some point in time. It's a pain. I just see the open source community not supporting that for long.
Anyway, above all of that, Microsoft has just released its Express line of products. They are all in Beta, but I believe these will all be free tools. So, why would Microsoft support a competitor whose tool would require new code, especially when it is so far behind Visual Studio? Life will only get better when VS 2005 is release. (By the way, the Express line will not include Team System.)