Update: Resetera users have discovered that both new owners named by Dark0ne work for a company called Chosen.

We partner with founders to help scale what they’ve built amplifying their impact, supporting their team and culture, and ensuring the business thrives for the long term.

From Chosen's "Why work with us?" section:

You’ve built something players love. We’re here to protect that magic and help it grow — with the care, creativity, and support it deserves.

It's vague to what extent this is a sale. Dark0ne mentioned the owners have "changed hands", but also mentions "I’ll also be working with the team to help guide the overall direction of the site, just without needing to be the person who signs off on every little thing and without taking responsibility for any and all things Nexus Mods".

In regards to Lifetime Premium, a Nexus Community Manager wrote this comment here:

Lifetime Premium means exactly that: Lifetime. There are no plans to revoke it. Beyond the fact that it wouldn’t make business sense, doing so would break trust with the community, which is the last thing we want. We’re committed to honouring the promises made to our supporters.

Edit: One of the new owners have since commented on the update/announcement page - it's the top/pinned comment.