As this is a EZY station: Some more details now on the opening of BER (please use your prefered auto-translator):
Probelauf: Tausende Freiwillige testen neuen Flughafen in Schönefeld - Berlin - Tagesspiegel
So all of TXL will have moved, the last stage during the night of 2nd to 3rd June 2012. Including fire-engines, so no plane can take-off anymore at TXL then. Not so clear about operations at the old SXF terminal. E.g. EZY SXF-LTN is bookable for 3rd June 2012, but will it be the old or the new terminal ? That might cause some confusion. You can get from one to the other by S-Bahn, but it takes a while (25min incl walking ?). One might think that they will still use the current SXF terminal, as getting all of the former TXL operations working at BER is tricky enough. ATC surely then will be already have moved to the BER tower (or is it even there already ?).
Speaking of ATC: Germany's ATC union is still threatening a strike (which was prohibited by a court last Thursday), the issues are far from resolved.