If Tomic gets his head together, he could be top 20. I see quite a few changes to the top 20 next year, but not so much the top 10. Every player in the top ten has some sort of consisteny to keep themselves within that rank. They're in their primes and that's their potential.
"I rest my case. Federer needs to win 28 slams, twice more than Nadal to be in the same conversation with Sampras." A famous quote from helloworld.