Today Matt, Madicken and myself went through the list of open issues and generated a list of issues that are currently blockers for releasing yt 3.5. You can see them here:
Some of these are harder than others and we may yet decide to punt on some of these.
If you are interested in helping out, please take a look at that list and send in a pull request for any of them. If you have a favorite pet issue you'd like to see fixed for 3.5 and you don't see it on this list, speak now or forever hold your peace.