psyflyer,
you will love it: berlin is PARTY at the moment!!! your train journey in 1st class will be luxurious (2nd class on ICE is perfectly fine, too), you will arrive in germany's newest train station, you exit the station and will be in the middle of the world cup party.
germany's last match is on sat evening (in stuttgart), but the team will go back to berlin to thank the fans... expect 1 mio people at lunchtime in the so called "fan meile" (fan walk), just facing brandenburger tor, cheering the team. well, you cannot miss it!

and after the final match, it will be party again, no matter who will win...