JA made one assumption in his calculations: He took the gap between Hamilton and Rosberg at the end of Lap 25 (which was 1.099s), but before Rosberg pitted on Lap 26 at the end of sector 2, that gap was down to 0.772s. The assumption he took was that the average pitstop time of the Mercedes team garage over the race, would be 22.7s.
Point being; 0.772s is a very very small gap. Over the course of lap 26, he closed that gap down by another 3 tenths. If you look at Rosbergs slow 3rd sector on lap 25 (the in-lap), he was doing a 22.421s, Hamilton, after his spin, on lap 28, with what I assume must have been shot tires due to the spin, did a 22.278s. If he had come in on Lap 27, and with perhaps a bit of luck with the pitstop, I'm fairly confident he could have been side-by-side to Rosberg coming out - and crucially, might have been on the corner inside.
It would have been really close, but IMO doable (with a bit of luck during the pitstop).