Whether or not the UN will be around or not is one thing, it being a relevent body is another thing.
As far as I can see, the UN has been a failure, and has almost NEVER been a significant organization. Now, there "may" have been a few cases that the UN stopped a war, made an international deal here and there, but overall, with the continue deteriation of, bascically the entire continent of Africa, their failure to disarm Iraq, the North Korean crisis, Rwanda, doing nothing in Bosnia (it was NATO and the US, NOT the UN), its a useless organization (funded by your tax dollars BTW [US pays the most and the US is the most bashed in this organization]).