If the Google Youtube API fiasco is any indication of Google's commitment to WP7 then I wouldn't expect much from Google on Windows Phone.
I think the YouTube API fiasco is a farce, because Google had no issues letting Microsoft use the YouTube API for the XB360 even though they compete with it via GoogleTV.
I think it was totally overblown.
Google has almost 50% smartphone marketshare via Android. They simply don't see a need to support OSes that aren't major players. Between iOS and Android 70%+ of the market is covered. That's enough for them.
They simply don't see a need, that's why.
Additionally, GMail sucks on ANYTHING without a Native GMail app. That's precicely why Google had the J2ME Gmail app for a long time, as well as the Blackberry app (now there's a BIS plugin so they dropped that). It's also precicely why they developed an iOS app with PUSH Notifications.
Even with ActiveSync GMail sucks because it's designed unlike traditional webmail systems for how it manages and organizes email.