1: As vB 3.8 is still in RC state, no tests have been done for compatibility, but as some people tend to upgrade vB before is goes gold, and at least some of those people probably also use PhotoPlog, what I can tell you is that I haven't received any incompatibility reports to date.
2: Yes, you can see it in action
here. The add-on that does that is
here (accessible after purchase).
3: No, there are currently no plans to import files from the vB albums into the PhotoPlog gallery.
4: Sorry, but I don't give ETAs. If I put a date out there, and then miss the deadline because of bugs or whatever reason, people might be disappointed or upset. What I can tell you is that the next version is a major rewrite and is in the works.