The problem is, unless Republicans can wise up and come to the conclusion that their days drawing the maps in Virginia are more or less finished, there is no way that amendment passes this year or even in 2019. At least up to this point, there has been no signs they are open to creating a fair process for redistricting, and I think they even shot down a redistricting reform bill earlier this year.
That means that the best Democrats could do, if they flip the legislature in 2019, is pass it in 2020, then they have to pass it again in 2021, and it would appear on the ballot in 2022, long after the maps are redrawn. However, technically Democrats could pass a regular bill creating an independent commission, but it could be repealed just the same too. I'm a little skeptical that Democrats in the legislature are going to pass actual reform, but I could just be pessimistic. Redistricting brings out the worst in politicians. It's far too powerful of a process to allow partisan actors to have any significant hand in, and it's perplexing how the framers didn't see this from the get-go (or did but foolishly left it in their hands anyway).
I dont think they ever imagined it could be so polarized.