The omen is certainly present. At the start of season five, Sheldon is still eleven years old and starts at East Texas Tech. according to the great explosionSheldon finds his father cheating at age 13, gets his master from Caltech at 14, and loses his father at age 14 as well.
Since he’s still at East Texas Tech at the end of Season 5, we’ll likely have some time before his father passes away. But since Chuck said that every season doesn’t have to be a year, it’s hard to know where we are in terms of age, but we an act I know George’s death is coming.