Actually, anyone that can create a wallet (a Core github fork or something new) that validates a single block (which is not validated on the existing chain) and only allows new blocks to be built upon the divergent block can create a hard-fork. Provided they can secure the hashrate to produce a single block (even if that block has to be created with a dif of 1 in order to be created), they can promise a hard-fork. Now, they cannot legitimately promise that said hard-fork will be adopted by anyone other than themselves, but anyone with more than 15 minutes on their hands can both promise and deliver a hard-fork..