This topic seems to come quite early - MySQL 5.0 (as GA release) is not even half a year old and MySQL 5.1 has just turned into beta.
But I've heard that MySQL 5.1 will be quite a quick release, so MySQL 5.2 is maybe not that far away.
So it could be a good moment to start to talk about the features that could be in MySQL 5.2. Some plans have already been published:
(if you know more sources, please add them as comments ;-))
Maybe, someone could create a new forum where people can discuss what they would like to see inside MySQL 5.2. I'm sure, many people inside the MySQL Community (me included) have their favourite features.