Any assurance that HODLcoin would still exist after every year?
regarding your first question: then the network continues on as-is, as long as there are active peers and miners.
regarding your second question: its kind of a silly question really. since the network isn't controlled by any one entity exclusively. the network can "exist" with as little as one accessible node.
I feel like your questions are more about if you'll be able to sell mined coins year after year, in which case I'd have to refer you to the exchanges as they all have their own set of rules for continued listing (some known, some not), and I doubt any of them can guarantee that any of their supported coins will be available year after year.