I just read this note by Gilad Bracha. It's very nice (albeit a little light on concrete details). Gilad's aim is to consider an OO platform for software services, paying particular attention to the programming language perspective.
I was pleasantly surprised to see Gilad talking about dynamic software updating - indeed it's core to his proposal.
I had thought that our UpgradeJ paper would be the last thing I did on DSU (or rather the journal version - still in progress - would be). Maybe it was more prescient than we realized :-)
Check out Gilad's paper for yourself!