if i were a betting man, i'd be willing to bet on him, but i wouldn't bet the farm, and i'd want some odds. 5 second improvements don't come easy in my experience...
i suppose i'm pissing in the wind by debating the meaning of "for sure," but the beauty of sport is that there really is no "for sure"--if anything, and i don't presume to be an expert on sub-4s just because i've done it, i'd also emphasize the difficulty of it. why cortes would be a "for sure" when other studs like hall, stember, meb, german, oshier (who basically soloed a 4-flat, but couldn't go sub 4 with verzbicas) and up to this point tamagno couldn't do it in h.s. is simply not obvious to me despite cortes' impressive kicking ability. is he really more of a talent than any of the names mentioned? who knows? but maybe ventolin and other speculators have a different meaning of "for sure" than i do...