My general sense is not many, but only Tesla would have the real numbers.
This late in the game (between 30-60 days from full reveal), there is really no benefit to canceling a reservation and losing one's place in line. There are fence sitters who are waiting to see what happens with options and pricing.
Both iPhone 4 and iPhone 5 prototypes elicited mass freakout/panic on Macrumors, with various people saying the prototypes must be fake.., terrible design blah blah. And then the 4 and 4s went on to propel iPhone to dominance. The 2012 iPhone 5 design proved so popular that it forms the basis of the 2016 iPhone SE (still sold today).
The Model 3 has the right exterior looks. The reaction to the sheet metal and proportions is nearly universally positive. It's the interior and single 15" display that is freaking some people out.
If Tesla's interior design turns out to be functional and charming despite the unconventional instrumentation, this will be their iPhone 4 moment. That's my intuition.