One Tesla tool they need —which Tesla released— is diagnostic sw to help ID the bad cell(s), else it would take longer to find a bad cell among ~1,500 of them.
As such their next gen pack is a single structural member of the car and likely will not be replaceable at all.
Tesla replaces battery packs and then sends the old one back to the factory to be refurbished, rather than junked.
As for future designs, a structural battery pack would still be replaceable. The difference is that the battery pack would supply a portion of the strength and rigidity of the frame. That doesn’t mean the car would fall apart if you removed it, however.