I know it seems completely unlikely at this point, but just think back to 2010.
If you were told that in 5 years time, Google would be partnering with a Chinese OEM for a Nexus smartphone, or that powerhouse companies like HTC and BlackBerry would be almost nonexistent in the mobile market, would you have believed it?
Anything can happen in five years. Samsung may or may not bow out of the mobile business. But as shown by HTC, BlackBerry, and Nokia, you are never on top forever.