Maybe a one-year deal with an option. But also, no rush, let's see how he plays the rest of the season. Segura's a good player but he may just be league average offensively by next year (and definitely by 2024). Even if you don't sign Turner you can probably still get 2.0 WAR at 2B from any number of cheaper players.
And yes, it's unlikely, but we're still paying a 2B pretty good $ next year too.
I'd pay the buyout and come back to him later, unless he takes the shortest team-friendliest deal at that point.