Do you mean when new extensions become available?
I would imagine that you will want to go to your preferences registry and search for email notification and also find out its offerings for prerelease registration. Almost all of these extensions come out in a tiered offering where companies have first dibs for their brand, then a premium price offering then it hits the shelfs. But more or less check with your reg. As I'm sure they will be more then happy to advertise to you!!!