I agree that you should do what feels right to you. Once the jam is over there are no restrictions and I'm not aware of any etiquette on the matter of updates.
I left my own game from last year's jam completely untouched, even leaving a very quick to fix bug that I still remember is in there. It had a lot of problems during development, so if I wanted to make something similar to it again it would be better to start over fresh.
This year I do plan to fix a lot of the bugs from the jam version and add a number of things I had wanted to put in or thought of afterward. I'll still leave the original version as a Windows download and the old WebGL build as a zip for archival purposes, though I highly doubt anyone will be looking at them after Monday. :)