Demo to Early Access
Progress and saves from the October Steam Next Fest demo do not carry over to Early Access. Plan to start again rather than choosing your Early Access character around a saved demo build.
Early Access to version 1.0
In an October 23 team response, XL_Don said the team did not plan on wiping between Early Access and 1.0.
That answers the announced direction: the plan was to retain progress. It is not an unconditional guarantee that no reset could ever be required.
Fresh servers and transfers
The later discussion of fresh 1.0 servers and possible transfer restrictions was a possibility, not a settled policy. There is no confirmed new-server or immediate-transfer arrangement to plan around from that discussion.
Resets during Early Access
The answer about the transition to 1.0 does not separately establish the rules for resets during Early Access. Treat those as different questions.
For the launch schedule, see release date and platforms.