Ehh not that much really, this happens to artists who pass and their family, labels the artist has had anything to do with, and rep companies start digging through past archival material. The artist Jimi Hendrix has had allot of post released material since his death in the early 70's. He was prolific in recording in the studio or some live show somewhere that had been captured for later editing for a live release or something. There are rumors and I don't know if they are true that there is studio recordings of Jimi Hendrix and Jim Morrison together doing some fooling around and it was captured on tape long ago before both their deaths later on but nothing has surfaced yet, at least officially.
The same happens to any artist who dies suddenly and leaves partially finished material or near completion material or just bits and pieces of songs unfinished. With the death of Jonny Winter I expect a rather lot of post release material to show up, what within the next 10 years maybe?
It does not really shake my world, I was never that big of a Michael Jackson fan, but it is kind of weird people pay more attention now that someone has kicked the bucket than when they where alive. Most people hardly give second thoughts while people are still living. It has kind of always baffled me but then again odd things humans do leave me pondering for hours sometimes when there is nothing good on the boob tube.