I added PIL to README couple of days ago because I saw latex output used it to create correct images (as latex only supports some image types).
It is not essential, and I fixed bug in latex generator, but did not test yet if images actually show (my test famtree of the moment did not have images).
So, not having PIL will just mean in latex output less pictures are available.
Then Doug uses it in webapp for something. So, this is not really a blocking issue, at most a minor feature we might loose.
As always in open source, for non-core functionality, it depends on developers interested in the functionality to maintain it going forward. If nobody does, exiv and PIL will be removed in the future.