There is a big drive by WordPress when it comes to plugins to keep them up to date, not use old plugins that haven't been updated for a while and so on.
This is a very sensible approach but in some ways it doesn't go far enough.
I have users of my plugin still using a version that was released over a year ago - it has bugs in it and features that are no longer needed or supported. I've tried to let people know through the support channels I have and I've even made one of the servers which it interacted with return a message about upgrading when calls are made to the obsoleted process. I know that several of these installs have been throwing errors for over 6 months so the people are obviously not looking at their settings, nor are they taking any notice of their updated plugins notifications.
What I would love to be able to do is basically turn those old versions of the plug-in off.
So if there was an option in the readme to put in a "Replaces" field which basically indicates that installed versions at the "Replace" version and below should be automatically de-activated (not deleted) in WordPress then it would really help.