I'll re-state my opinion here. In my 30-plus years of dealing with first-time jumpers, my educated guess is that Cooper pulls the ripcord. With pretty much any parachute, but especially with a rigger-packed emergency chute, if he pulls he all but assuredly gets under an open canopy, regardless of his body position. This is consistent with Andrade's research on WWII bailouts.
However, with a basic round parachute over possibly inhospitable terrain, there is the possibility of his getting injured on landing and being unable to hike out. The likelihood of that would depend on exactly where he jumped and what was the terrain. What is the ratio of rocky hillsides/trees/water below him vs flatter open fields. If he's in an open field, he's probably ok. If he's in worse terrain, he might still be ok, but maybe not.