Here's the thing, those backers could pull out if they wanted before the kickstarter ends. What if the whales decide that it's not in their interest to do so, or perceive Sony as funding it and, as it's already smashed through its funding goal, back out?
It will be interesting to see if the number plateaus or peters off.
That could happen in any Kickstarter, but almost never does. Bloodstained was revealed to be published by Deep Silver (with confusion over whether they own the IP) halfway through the campaign and it still made every goal they set.
The people that most want Shenmue 3, really want Shenmue 3. Those people aren't going to back out. It will slow down in the middle like all Kickstarter projects do, and depending on how hard they push toward the end it may or may not pick up again.