It depends on the target. If this is a server, then you could potentially keep multiple copies of Guava in your lib (with different namespaces) and use the appropriate one (this will also require some jiggering with the compile flags for various modules to make sure the right one gets pulled in). It'll add a lot of bloat, but that may not matter.

If you're deploying to Android... you're kinda screwed. You can't afford the space to duplicate.

Honestly, I think the best way is the facebook/google way here - upgrade frequently and aggressively. Which might not be helpful advice after a long time of not doing exactly that.