WebStorm, maybe. But it won't be a real threat to IntelliJ until around the same time as it's a real threat to Visual Studio (full version).
Which killer feature of VSC does IntelliJ lack?
Not locking most of the UI and saying it's "indexing..." every time something changes.
Being a text editor it is less bloated/faster.
Feature wise I dont think VSC cant beat IntelliJ.
Does VSC have refactoring?
Microsoft employee here. Some basic refactoring feature is actually supported, such as rename. Of course there're a lot of other coding assistance and refactoring features could be added, we plan to further improve the Java experience, including editing, on VS Code in next months together with Red Hat and other community members.