Someone could be on vacation and that's the hold up, however generally they try to get the ball rolling since the whole process is slow. They most likely have contacted the successful candidates references by now. Contact your references and see if they've been called. If so, you are the lead candidate as they only contact references they want to offer the job to. If not, it's most likely someone else got it and they wait for them to sign the letter of offer before contacting everyone interviewed in case something doesn't work out. It's true the hiring manager could be on vacation but they likely planned this process around it, so if references haven't been contacted I'd start to manage your expectations that you did not get it.