First off, we expect GMail 2.0 to go live later this year. We're also expecting that it will feature tighter integration with existing Google services:
“Initial testers reported the test version felt noticeably faster and more responsive, particularly in contacts management. They report a new contacts screen, as well as that the chat can now not be hidden (at least in the trial version).
Another improvements is that contact pictures can be transferred directly from Google's Picasa web albums, all server-side, to reduce bandwidth and processing expenses on the user side.”
We are expecting that the upgrade will still retain IMAP compliance, and we wouldn't be alarmed if Google added even more storage capacity.