Hi,
It depends.
That value is what is used to link everything else with an order status.
So for example, if you have "confirmed" in that field, you'll have it also in the "order_status" field of all the orders with that status selected, but also in the hikashop_config table for the different settings configured in the System>Order statuses listing.
So if you change that value in the hikashop_orderstatus table without also updating the orders and settings where it is used, you'll end up with orders with an unknown order status and settings not linked to the new namekey.
It probably won't crash anything, but it could be problematic. For example, if payment methods use that status on the orders when a payment notification is received, then the orders' status will be changed to that old namekey and thus not linked to a known order status and the processes after an order is confirmed might not be triggered (email notifications, stock update, mass actions, etc).
So for the orders, you'll have to update the order_status, either with a MySQL query or a mass action, and for the settings, you'll have to reconfigure them with the new status.
All in all, it's sensitive, especially for the main ones used through the whole shop, and that's precisely why we don't allow you to change order statuses' namekey, only create new ones.