All Hemsworth has done is say that he'd like to continue. That's all.
There's no guarantee that Marvel will renew his contract, and there's no guarantee what role he and Thor will take if they do decide to renew.
At the moment, Hemsworth is only contracted to appear in one more film after Love and Blunders. That could be Thor 5, or it could be Guardians 3.
If Jane Thor is successful, Marvel may decide to cut their wages bill by not having Hemsworth around. After all, they'd still have *a* Thor.
On the other hand they may decide to recontract Hemsworth to play Thor only as a second-fiddle character, appearing in Guardians of the Galaxy and Avengers films, and as a guest star in Jane Thor films.
Any way you want to cut it, there's nothing official here. I doubt if Marvel will even begin to renegotiate with Hemsworth until they've seen how the public reacts to Natalie Portman's Thor. In other words, until they've seen the box office for Love and Thunder.
At this point, I think Hemsworth's only hope is if Love and Thunder tanks.
Portman doesn't have the pull/draw that blockbuster movies demand. Her thing is more the Black Swan type movie that she did.
So, I think it's safe to say that Hemsworth has nothing to worry about with contract extensions/renegotiations