edit post permalink

I have a very popular page on my review site. It’s basically the best item of 2013. Well now it’s 2014 so instead of writing a whole new post i edited the permalink on the edit page link and now traffic has crashed as well as I see both pages in google webmaster tools. I am wondering if this is the cause of the traffic crash due to Google possibly believing that this is two posts thus duplicate content. So I am wondering if I should leave things the way they are for awhile and see what happens or delete the post entirley. Then how do I totally get if out of the serps because I would eventually like to repost it at some point in time.