More modest suggestions for bug trackers
I consider all of these to be corollaries to my first set of modest suggestions, or more exactly to the core idea behind my suggestions, that being that you should arrange it so that the open issues in your bug tracker are things that you are fixing, not wishlist items, not things that are maybe going to be fixed some time in the future. Stuff you are fixing now, or close to now.
This implies that you need a way to explicitly defer issues, in order to deal with things that you know are bugs, that you want to deal with at some point but which you are certainly not going to deal with now or deal with before the next release or whatever. To make this easy to use, the bug tracker should have the idea of 'events'. When an event happens (such as 'release1.1'), it triggers actions like automatically un-deferring issues that have been deferred until the release happened.
(If maintainers have to manually un-defer deferred bugs, they will either never defer bugs because it's too much of a pain to un-defer them later or they will never un-defer bugs that have gotten deferred.)
You could also use the same machinery to automatically close at least some sort of bugs that had been filed against the old version (thus copying what some people do by hand).
In general, I think that maintainers should be encourages to aggressively close (or defer) bug reports if they are not going to deal with them more or less right now. As cruel as it is, I think it's better to push the burden of re-filing or re-opening issues off to the people with the problems instead of the people trying to fix them. At the same time, bug trackers should make it easy (but perhaps not too easy) for people to redo bug reports without having to reenter them from complete scratch.
(If you make it too easy for people to redo or reopen old bugs, they won't confirm that their old bugs are still there in your current version before re-opening them. This leads to bug reports for issues that don't exist any more, which causes maintainers to start ignoring your bug tracker. We all know where that leads.)