Legal Question in Real Estate Law in California

I don't fully understand your question but if you want a month to month rental agreement when your lease expires, then to be clear, enter into a written month to month rental agreement. If you want another lease agreement with your tenant, then you can just renew the lease you now have (providing you are comfortable with the terms and conditions). If you wish to add or delete certain provisions of your existing lease, then enter into a new lease with your changes.

Whether it is sound practice or not, I know a lot of landlords (including myself) and at least one successful professional property manager who do not bother to write replacement leases with tenants who initially moved in on one-year leases, at least for residential properties.

It is up to you. Your tenancy will become month to month, and can be terminated by the landlord with sixty (60) days notice, or 30 days depending on other circumstances which are beyond the scope of the facts that you gave. Entering into a new lease would buy you some protection in that it would create a new tenancy for a fixed term, rather than a periodic tenancy. This may buy you time, if you don't want to move out right away, but will also put you on the hook if you want to leave early.