Thankfully, most likely nothing will reset when Early Access ends. iA isn’t confident enough to say that this is guaranteed, though.
Support website:
Accounts which have one or more purchases associated with them are never reset, even if they become inactive.
Some account progress might be lost if it ever becomes necessary to roll back to an earlier snapshot of the game database, but even in such cases, we’ll take extra care to preserve all purchases.
All of your account data is kept on the game’s servers. The only thing you save locally is a small token (which tells the servers which data is yours). This consumes CPU time (because your account data needs to be indexed and searched), storage space (on the disk and the database), and network bandwidth (because it must be transmitted to other players). All of these things come both at a technical and an economic cost. This makes it necessary to periodically clear out inactive accounts. Typically this happens after 6-12 months of inactivity, but under certain circumstances the period could be shorter (if you have only played for a few minutes total, for example).
Accounts which have a purchase associated with them will never be reset.
The only reason you can lose an account is being inactive for 6-12 months (currently, only the 12-month mark is enforced) and did not make a purchase.