It looks like the Diablo 3 v1.0.7 patch will indeed be with us soon and the there will be a PTR to test out the changes. A lengthy session of Blue posts by Vaneras on the EU forums state:
There have been quite a few requests (demands even) recently for more player-testing of content before we release it, and we would like to accommodate that whenever it makes sense to do so. A downside when player-testing is involved is that more time is required before content can be released, but we are of course trying to find a good balance on that so that the wait for new content is not unreasonably long.
I am unfortunately not yet able to provide any specifics on the content that will be tested, but it does look to be a sizeable patch
Also, the Diablo III PvP Update blog mentions that dueling is currently scheduled to release with patch 1.0.7, so hopefully (if all goes well) you guys should be able to get some testing done on that.
At this point there is still no ETA on when the patch will arrive but at least we know there will be some sort of test period before the final version is released. Vaeflare also added the following on the PvP blog update we’re all waiting for: