The major traffic sources are not going anywhere anytime soon. Bing, FB, and Google among others are going to be excellent traffic sources for the foreseeable future.
However, these platforms are also getting more difficult to use for CPA and affiliate marketers. They are constantly taking steps to limit affiliates to ensure quality content for their platform and competition is increasing prices.Sure, you can constantly adapt and bend to their rules to keep thriving. There is nothing wrong with that. However, it is a constant battle just to be able to use them. So even when you are crushing it with them, you will always be worrying if you are doing enough to stay.