Usage of OS 6.0 in February was only up slightly from the month before. The increase was only a little under 1.4% and the growth of OS 5.0+ was even smaller. RIM is continuing to not make these upgrades as much as a priority as they should, and it is looking doubtful that there will be any more significant growth until OS 6.1 is released this summer.
This data is taken from downloads of the popular BlackBerry strategy game Pixelated. Data starts from the release of version 2.0 in April of 2010, and goes through the end of last month.