I imagine that battery development is pretty much understood by Tesla, probably more than most, so the testing and ramp up will take as long as a lot of people believe, actually. But you seem to forget that range, although important, is balanced by COST. Tesla must hold costs down as much as possible, competing against "cheap" products like the Ford F150. A lot of truck owners whose business is mainly in "the city" do not need 500 miles of range, so Tesla plans to offer choices, so it's not ALL about range.
We don't have a fully developed idea as to how long a CT will last. Most work trucks don't last 200,000 miles, and conversely, most work trucks don't travel very far, doing jobs in the home town rather than in the next state. No reason to believe an electric vehicle won't last 20 years/500,000 miles under these circumstances.
New battery tech is NOT critical, "IMHO". One can use "OLD" battery tech and get the range, as is evidenced by my Model S with 400+ miles of range. All it takes is more batteries. Have you heard data on how much new batteries weigh for the same kWh as compared to old batteries, for example? Sure, new batteries will give some advantages, but by the time the CT is ten years old I'd imagine there will be several new battery developments.
And Gigafactory TX will come right along. They've already built Gigafactory NV, so there's not much learning curve. But we'll see, won't we?
