They just extrapolate those dates based on the average intevrals of previous updates. Nothing you should get excited or worried about. If it happens, it happens.
I hope it doesn't come for a few weeks, same with PR! Just so we all get enough time to get our contest sites PR and back-links!!
are you saying the algos will change the rules on BLs or wil more of the BLs be showing when you check for BLs in google?