News article here, I doubt there is any serious consideration for this to let it decay.
The article is long, there are 2 guys presenting their oppose views, I did not post this but here is the link on the bottom, also I guess might as well make a poll of it.

Should Auschwitz be left to decay?

On the eve of Holocaust Memorial Day, two experts on Auschwitz argue for and against the idea that the former Nazi death camp should be allowed to crumble away.

Historian Robert Jan Van Pelt says that once the last survivor has died it should be left for nature to reclaim, and eventually forgotten.

But former Polish Foreign Minister Wladyslaw Bartoszewski, once an inmate, says Auschwitz must be preserved to bear witness to the fate of its victims.

http://news.bbc.co.uk/1/hi/world/europe/7827534.stm