Yeah, noticed that too. In fact was going to post this to what did just update thread, but you posted the change first here in this thread. :-). However, here goes an abridged version(I thought I had copied the post, but in fact I didn't, so I write it again :-/)
I tried to wishlist something previously and couldn't- and then noticed I had been logged out just like that. I tried to log back in and was greeted by a new, more modern login screen(see attachment-the blacked part is my email- I don't want to show such sensitive information!). My guess is this is the first sign of the long rumored site-wide redesign.