There is already an exhibition there which is open to the public, so you don't have to wait untill 2015 - however you have to register first if you want to attend a guided tour:
(I edited the phone number, so international visitors may be able to call)
Here is another fine article about the openening, where also an Irish sailor, who was a POW at Valentin, attended:
http://www.weser-kurier.de/Artikel/B...eroeffnet.html

to the sailor, Harry Callan
And a link to a photo series of the bunker:
http://www.weser-kurier.de/Bilder/Br...-Valentin.html