PO hasn't been forgotten or abandoned, despite the lack of updates here. The reason no new features have been developed stems from the fact that PO pretty much does what I need, and does it without fuss or complaint.
The vast majority of the feature wish list involves a great deal of disruptive effort, and I haven't been able to justify that level of effort for a project that comes out of my limited spare time.
So, while I'm not abandoning PO (after all, my personal repository has over 116,000 images!), PO will remain in “stable maintenance” mode for the foreseeable future.