When do you think the structural battery pack and 4680 cells are coming to the Model Y?
When Austin is up and running? When will Austin be doing volume production of the Y? Is Tesla going to begin production in Austin with 4680 packs or 2170 packs trucked over from Nevada?
Why are folks not waiting until the 4680 cells to order their Model Y?
Won't these 4680 cells provide greater range and charging speed benefits? But, perhaps, most significantly, longevity of the pack?
The new just-started-production Model S and Model X were redesigned using the original size 18650 cells, and are getting amazing performance, range and longevity using that size.
The primary advantage of using a larger cell is that fewer of them need to be made and handled during assembly. There is only a trivial density advantage using a larger cells, and a significant increase in the thermal and electrical path unless the design is changed to mitigate those problems.
If your battery factories are already at their production limit, it's really appealing to build larger cells. They take only slightly more time and space to manufacture, and handling fewer cells per vehicle simplifies every subsequent manufacturing step.
But as an end-user, there is minimal advantage to the larger form factor. Using the same build techniques and chemistry with the existing 2170 size would result in a superior battery.
Finally, you might have the wrong idea about longevity. If you want known long life, you want the current pack design. Experience has shown the current batteries are going to last the expected life of the vehicle with only a modest drop in performance. You should stay away from structural packs until there is enough real-world data to show that flexing the cell casing doesn't cause physical wear or capacity loss.