A little buzz yesterday/today about this... Looks like Google is cleaning out stock to make way for the new. If you need a new replacement Nexus 5, good luck!
Let us know if you are able to get a replacement, but don't drop your phone just to try and get a new one...

Google May Replace Your Broken Nexus 5 For Free Under A New 'Unofficial' Warranty Policy

Yes, Google Will Now (Probably) Replace Your Nexus 5 If You Bust The Screen | TechCrunch

Google starts replacing damaged Nexus 5 phones for free | 9to5Google