There are certain new gTLD extensions that could be extinct (I believe) in a number of years. Mostly, looking at ntldstats, I see that there are 1185 extension out of which 726 have less than 1,000 registration. While most of these are a .company(name of the company) extension, some like .data and .hair have only 1 registration each. I believe, when it is time to renew the contract, these tlds will become extinct. Definitely, 50% of the bottom with <1000 registrations(generic and not a company tld), would be extinct. What all extensions do you think, won't survive in 10 years from now?