Most alternative domain name systems nest everything under a single TLD – .eth, .onion, etc. In theory, either the standard DNS or a different alternative name

Most alternative domain name systems nest everything under a single TLD – .eth, .onion, etc. In theory, either the standard DNS or a different alternative name system could cause a conflict by using the same TLD themselves. But unsurprisingly, ICANN/IETF are a lot more receptive to "please avoid using this one semi-branded TLD" than "please hand over the entire namespace to us". .onion is already formally reserved by IETF RFC as a "special-use domain name", and hopefully .eth will join it in the future. As for a different alternative name system, conflict over .eth could theoretically happen if Ethereum forks again or if ENS itself is somehow forked, but an independent effort would presumably pick a different name.