I also want to find a way to upgrade to 4.9. Mint is great and all but the kde support isn't very good. Well, can't really blame mint for that, I guess its mostly debian to blame as its very slow to update to the latest versions of kde. If only there was better kde support in mint debian, one option I've seen is that you can build from source, will need to visit the kde website to get more information on that if interested and prepared to do a bit of coding. Otherwise I am still exploring other possible options available. Wonder if it will now be available in debian sid, kde is already releasing 4.10 RC, surely 4.9 should now be available in sid.