I did manage to get access to an Xmarks account, and I am going to try to get Xmarks import ready in time for that service's demise on May 1. In order to ensure that Xmarks users will find their data can be organized in a way they expect, I will also need to add a new feature to LinkLocker itself: a means of organizing links into categories. Adding a hierarchical categorization structure is probably good idea generally, and this situation with Xmarks provides a good opportunity to build it.
The question is whether I can meet the deadline set by Xmarks' shutdown on May 1. I'll give it a go.