Well, it looks like Keye and I are making yet another round of changes to the Online Proofing System. I think I've put more hours into that job than everything else combined. :D
Anywho, we're going to try revamping the commenting system completely, allowing people to zoom around the element and draw on it just like you would in Photoshop or something. This should alleviate some of the time it takes to post some of the smaller comments. Additionally, the look and feel of the navigation will change a bit because it seems a little childish at this point. And finally, you'll be able to upload huge files. Hopefully you won't do it all the time, but the ability will be there.
As far as timing goes, all of the changes except the commenting system are finished and awaiting testing/deployment. The commenting revision, however, will take longer; probably a couple months. BUT, if all goes as planned, it should be well worth it!
Stay tuned!