Now that once permanent tattoos can be removed, that means they are no longer permanent.
So is it now permissible to get a tattoo, why, why not?
The sin is not the permanent state of the tattoo. The sin is committed while you are drawing the tattoo. Leviticus 19:28: “You shall not etch a tattoo on yourselves.”
There is an interesting article Rabbi Dr. Ari Zivotofsky from OU. https://www.ou.org/torah/machshava/tzarich-iyun/tzarich_iyun_jews_with_tattoos/ he discusses a lot of points and opinions on temporary tattoos.
"Permanent" means "will last forever without undergoing any special procedure."
Rabbi Moshe Feinstein writes that even though a tubal ligation can be surgically reversed, it's prohibited as "permanent castration" for precisely this reason.