Having read that link, the wording is ambiguous as to warranties.
"Model S comes standard with a Four Year, 50,000 mile New Vehicle Warranty. An additional Four Year, 50,000 mile Extended Warranty will now be available for $2,500. Please note, this is a “Four Year” Extended Warranty, not two or three years like most Extended Warranties. You will be able to purchase this option through your MyTesla page in the near future.".
Does additional mean, a time extension ... an additional 4 years, OR a superset warranty for the first 4?
One can easily read this to suggest that the first four years no longer cost $600 per year (before discount) ... and is the warranty still void if you do not pony up?
Admittedly, further on it states, "Several months ago we announced a Four Year, up to 50,000 Mile Prepaid Maintenance program for $1,900, or $2,400 with unlimited Tesla Ranger visits. ".