I’ve been thinking about this for a while now, what happens when David Bateson becomes unable to voice agent 47 anymore? Some will say that the franchise will effectively die without him which I disagree with, but what cannot happen is someone else voices 47. If I had to decide what to do in this situation, I would say make one final game where you play as a character such as Lucas Grey and since its the final game, you can make a much more interesting and dramatic story. For example, 47 and Diana expose the ICA (for whatever reason) to the world and you get arrested(good opportunity for a prison mission) but after this you may seek vengeance on 47 and Diana and the final mission will force you to eliminate them both. A cool idea would be to try to identify 47 as he will be disguised and hiding. The mission could have 2 endings:
You eliminate 47 and escape the law searching for you. The ICA has collapsed and imploded on itself so you escape to your family.
47 eliminates you. The ending cutscene fades to your funeral with your family looking on and crying. But 47 watches from a distance. The final scene shows 47 throwing his silver ballers onto a fire and vowing to leave the assassin life behind.
47 could be voiced by a skilled impersonator. I saw a video a long time ago of someone perfectly imitating 47s voice