Page 2 has discussion relevant to this.
The Elon quote requires Li-ion pricing below $100/kWh. This was previously forecast for 2024
For whole pack replacements with refurbished units and a returned bad unit, I don't see prices dropping a lot. Refurb units don't depend on new material costs that much. Historically, we haven't seen Tesla extend highly discounted battery costs to the customer years down the road. I don't think there's a precedent for cutting the cost substantially.
For new material, you're looking at either brand new manufactured units or remanufacturing your own pack with fresh modules. Brand new packs are unlikely, as they are needed for new vehicle sales. So you're stuck with remanufacture, if they ever offer it. While this may be cheaper in parts, it's a heck of a lot more labour. There's also shipping involved since they can't/won't unseal the packs at Service Centres.