This way lies madness
The DNS does not need, nor even benefit from, a TLD for every niche, interest and societal sector. Technically, the system would work fine with no TLDs at all. They were conceived to help organize the DNS around the purpose and function of the domains under them, but aside from .GOV and .EDU, for which you still have to provably qualify (and setting aside the country-code domains for the moment), the rest have been stripped of their meaning entirely.
Remember when .com, .net and .org meant something? To get a domain you had to include a short written justification (and $100 USD) wth the application, and that had to match up with the TLD you requested. Strictly, you got .NET if you were a part of the Internet itself, .ORG if you were a non-profit or .COM otherwise (granted, the was a lot of play in the system, but that was the goal). If .com, .org and .net were merged into a single TLD there would be no harm in that at all; they mean nothing any more. Even USENET's top-level groups are more meaningful.
TLDs are not directories; they are not browseable; being part of .autopartsdealers* isn't going to get anyone to your store's site any faster than if it's www.south-booswah-autoparts.com--in fact, less so. I see no reason to waste time and trouble over this; it's headed in the wrong direction. These new "niche" TLDs will soon be full of inappropriate domains just as .COM .NET and .ORG are now, if we imagine for a moment that those old standards still existed. It's just complicating the DNS and creating illusory significance to the domains under them.
(I was going to say .hamster-duct-tape, but that would be lost on most people.)