There has been a rumor going around for a long while now about inactive gamertags getting reset/released. So I finally took it upon myself to figure out if this is true or not, but unfortunately it is not
I contacted Microsoft on the support chat and asked if they will be releasing gamertags, and he said they cannot do that simply because of the terms of service. So if there is a gamertag you want then you will have to find a way to get ahold of it. I do have pictures of the chat but they are on my phone and I don't know how to upload them on here.