I installed and enabled Entity translation and Entity translation upgrade. After playing with the functionality using my (almost empty) test site, I tried to uninstall the module. (Not that I did not like it, — the functionality is OK, I just wanted to check various things under the base install without any contributed modules.) After disabling both ET and ET upgrade, I went to Uninstall tab under Modules, unisnstalled ET upgrade, then ET, and... I still see both under Modules->List. When I select Uninstall again, it says there is nothing that can be uninstalled (or, when there are other modules that can, the Uninstall tab shows those other modules only, without ET and ET upgrade).
I actually tried both alpha1 and dev, and it happens exactly the same way to any of the two versions.
Francesco, I can provide access to my test installation if needed, so that you could play with it if you need to check something.