OK, the verdict is in.
According to the Car and Driver instrumented test (thanks to Anticitizen13.7 for posting) the weight of the 70D is 4608lbs, while the weight of now defunct 60D was essentially the same - 4597lbs according to the Road & Track data back from Oct. 9 article published right after the "D" event. This is consistent with my theory that the battery in 70D weighs the same as the battery in 60, contains the same quantity of cells, but each cell, due to higher volumetric and gravimetric energy density contains about 16.7% more energy. This is consistent with the conclusion that 70D contains new generation of the cells, due to show up in Model X, and, perhaps a little later in other variants of Model S.
Hello 300+ EPA range in Model S??
I'm going to play devil's advocate here... are we concluding based off two different weight measurements by two separate entities several months apart? We also don't know the trim levels, accessories, tires/rims for either test.
As much as I hope they have moved to a newer chemistry, we also have evidence from a 'spokesperson' that it's specifically more cells, not newer cells. 2015 Tesla Model S 70D: First Drive Of New Electric Car Base Model (Page 3) I'm not saying this article/source is necessarily correct, but I think we need more evidence before we can come to a conclusion.