I had a look at the warranty and it says that they will not install a new battery, just one that gets you to the minimum of the promised degradation range:

  > For warranty claims specific to Battery capacity, the replacement Battery will be in a condition appropriate to the age and mileage of the vehicle sufficient to achieve or exceed the minimum Battery capacity for the remainder of the warranty period of the original Battery. Note that the vehicle’s range estimates are an imperfect measure of Battery capacity because they are affected by additional factors separate from Battery capacity. The measurement method used to determine Battery capacity, and the decision of whether to repair, replace, or provide reconditioned or remanufactured parts, and the condition of any such replaced, reconditioned or remanufactured parts, are at the sole discretion of Tesla.

https://www.tesla.com/sites/default/files/downloads/Model_3_...