I think half would be quite optimistic. This is a free option play for anyone who wants to daydream about buying a Tesla and who can scrape together a $100 callable loan. The bar was higher with the Model 3, at $1000, so I would expect the conversion rate of actual buyers with a 90% smaller deposit would be even lower than it was with the 3.
I'm sure Tesla loves it when the media claims they have $10B is "pre-orders". The reality is no contracts have been signed, no revenue generated, and they're 2 years from production (ignoring Elon time).
I am keeping an open mind, but I need to see range predicts when the truck is being used as a truck. Even with the max range model, can I load the family in it and a bunch of gear and make it to the mountains and back on one charge, factoring in ambient temps and the changes in elevation? What if I'm pulling a small toy hauler with a couple quads? Or maybe most buyers don't care about that. Too many trucks out there being used as grocery getters and this one might be the biggest offender ever made.
All that said, the calls and the logic behind them were a darn good play.