Very well could be part of Amazon's goal.
But I think the only way to really tell about publishers is if Simon & Schuster also makes those 5,000 books available to Fictionwise and everyone else.
Maybe they did and Amazon got the headline because more people have heard of them. Maybe S&S announced it for the Kindle since Jeff Bezos was there. Maybe Fictionwise (et al) is on the phone with S&S right now negotiating a similar deal.
We just don't know yet.
If not, or if so, then we will be better able to see what is happening.