I’ve recently upgraded a client switch 4500 with sup 6l-e to the latest software and it was one of the worse decisions i’ve taken in my life. Without going into too much details, a lot of people had to go home on two days in a row because of problems with dot1x authentications of APs and ip phones.
A word of advice, therefore: do not be too hasty in your upgrades. Wait until others have upgraded, read forums, talk to other admins. If there’s a serious vulnerability in your current software, try to make sure it cannot be exploited via some other measures than an upgrade to a possibly unstable version.
Ideally, create a test lab where you test client configurations.
***do not use version 15.2(2)E7 on your 4500s.***