IMHO lifting of the sanctions should be tied to a complete withdrawal of all forces from Ukraine by Russia, not tied to the Russians replacing Putin.
You want an incentive to end this thing, and you don't want to drag on policies which will only inflame the Russian people (as happened to the Germans post-Treaty of Versailles), and which we know are hurting the Russian people more than Putin.
What's the point of keeping the sanctions on, if Russia fully withdraws?