There's no technical barrier to doing so. I uploaded new files to my project page and they also appeared on the submission page. This isn't just because it's my own game; there are a few other submissions with post-jam updates and alternate versions that show up in the submission pages for me as well. If you need my to, I'll take mine down, and I'm sure the other jammers will as well if they're not passed out exhausted, but it's an entirely voluntary/manual thing.