As I mentioned to Mike (Gollum) you are assuming that battery technology will not evolve but remain static. This is not true.
The share of the battery market that remains lead and acid is shrinking, furthermore new technology is being developed, and now that it's backed by VC funding, is gaining serious momentum. The latest development is silicon plating batteries which is a lot less toxic. There's also something called the "Jesus Battery" which is cutting edge technology in that it is solid state polymer. Yes you read that right, polymer, as in plastic. I think we're going to move towards that- towards using silicon in anodes rather than graphite. There's also nanowiring technology which will not only substantially extend battery life, but withstand hundreds of thousands of charges without weakening. There's also the foam battery- I could go on and on, but you get the idea.
And as far as Elon Musk, I am no fan of his hubris or attempt to corner the EV market or to retain proprietorship on his Teslas by refusing to sell spare parts, diagnostic tools and even repair manuals, not just for his EV, but his house products. This puts him in the "big boys" category.
However he did give EV and battery technology a big shot in the arm with his PT Barnum style- and not only made the other big auto companies see the potential of this market, but forced them to become major players.
Once they catch up, I expect Tesla to become obsolete or a fringe player.