Why should we leave apache common collection?
There are several reasons to change the collections framework.
Since the apache collections should be backward compatible it would not be possible to change to a actual Java version. It would be necessary to change to another collection framework (or write all the stuff by yourself).
There are several projects which created a collections framework by themselves or took the apache collection library and upgraded it with generics.
Guava is a project like the apache commons. Since a few weeks the Google collection project is now in the guava project integrated.
I just will take a view to the collection package in the guava library.
What is in the guava-collection?
Helper classes for:

google, Java Collections, Google, Guava, Java