Sorry, we also do not know when 2G will be turned off for good. We believe however that in Germany and most of Europe 2G will remain the fall back solution. Technically it makes more sense to turn off 3G before 2G. Main reason being that there are numerous technical devices (machines, meter, control systems) depend on 2G. All together there is a higher demand to keep 2G alive than 3G. I personally expect we will see 2G for at least 5 more years in Europe.
As far as the upgrade from 2G to 4G is concerned that is unfortunately not an option. The hardware is totally different so there is no upgrade possible.