He was already mortally wounded in the Pelican, and even if he jumped out of the Pelican he would have fallen several hundred meters in an area where the Covenant were rapidly closing in. He'd then have the problem of a destroyed Scarab crushing him. Even if he survived all that, why on earth would he not contact Six and Emile, or have Auntie Dot do it, to inform them that he's still alive? No. He's canonically dead and no amount of 'but what ifs' are going to change that.