I really don’t want to see him die. I’d prefer if he were to personally train a successor. Then that successor would take over where he left off. It could be that MC would be able to communicate to the successor via comlink or AI.
At some point, it the franchise goes past this trilogy, MC is going to have to take a back seat. But why kill him.
Take a look at Batman Beyond for instance. Bruce Wayne is no longer Batman, yet he still is in charge. He trains a young man to become the new Batman and through him we get to continue the adventures of Batman, even though it’s not Bruce Wayne at the forefront.
It’s already been publicly stated that there will be a young soldier who is inspired by MC. That soldier is on the Infinity and eventually becomes a leader. I suspect that this solider will be MC’s successor. (Not replacement, noone can truly replace the Chief)
Gawd, what if Chief is cloned and becomes an AI? Would he then have more of a relationship with Cortana (who I’m assuming will find a way to beat rampancy). The AI Chief could then escort the successor on mission. So we’d still have chief to a point, just not as a playable character, unless in some virtual AI mission.