Is Facebook Going to Continue to Focus on Developing a Great User Experience?

I don't actually think it's necessarily going to be detrimental to the user experience using the product at all. And in fact, the case you've just mounted is exactly the case as to why they're going to continue to focus on developing a great user experience. The point at which the departure happens is when Facebook is forced to prioritize the interests of the people paying money versus the interest of the people using the service. That's where the problem lies. You are not the customer, you are the product, and they're happy to keep you that they'll do whatever it's necessary to keep you round as the product. Don't be under any illusions that they have your best interests at heart