Sasha has now not been seen for over two years. It is not impossible that she is still out there and has moved to a new territory, however she was very old and was behaving oddly the last time she was seen, so it seems likely that her time had come.
While I don't want to single out Sasha over any of the other possums in the area, she has lived here longer, and had more babies, than any other possum, and she deserves to have her life celebrated. She does not deserve to fade into obscurity once the blog mentions stop.