If you choose to let your subscription expire you will lose access to the ability to download updates; so there’s a big incentive to keep paying, especially if you play with friends… but since not downloading updates means it’s not costing us anything, I really don’t have a problem with letting people play without keeping their subscription active.
It’s definitely sandbox. There are quests in the game, and in the future there will be long and even epic quest lines… but right now and continuing for the life of the game, it will be more of a sandbox environment where players will (eventually) be able to choose what kind of character they want to be, what their backstory is, and where they start. It’s then up to you to interact with the world as you see fit, and seek or stumble upon the quest lines.
The basic idea is that you’re not necessarily the chosen one. Most games force you into the role of savior, hero, Dovahkiin, etc - and while that’s great and not necessarily a bad thing, I wanted to do something different. The core concept of the game has an equally strong non-violent, non-adventuring component to it… so if you want to be a shopkeeper and sell crafted goods, or homestead somewhere in the wilderness, you can do that as a focus, rather than a distraction… or you can go and fight monsters and bandits and uncover legendary treasure etc.
The cool thing, in my opinion, is how this rolls over into multiple players. You can still have the core, unique gameplay that you get in a single-player game (As opposed to the weaker content you tend to get with MMOs), but playing co-op you can focus and do party builds that aren’t necessarily an option when playing a game by yourself (For instance, you can be a cleric with virtually no offensive capabilities)… or you can have a player that holds the fort down and constructs an ever improving mansion, while the other players go off adventuring.
We’re definitely still a long way out from that… but that’s the general direction that you’re going to see the game growing in.