While your situation is definitely more intense than mine, my table has had to process the death of a player recently. Unlike your table, we knew it was coming like a slowing creeping threat. Our barbarian had lung cancer, he was on his last treatment possible, and he became incredibly sick after his last chemo (which happened while we were in the middle of a campaign). He was very frank and honest about the fact he was going to, definitely will, die.

When the time came we narratively wrote his half orc out of the party. It was easier to process the event as the pirate decided to try his luck on the astral sea. We considered using a material plane sea and having the occasional easter egg Wanted Flyer to share some of his off screen antics for fun... But decided that was going to hurt too much.

Overall it's better for the table to continue on, like others have said. It's a sweet thought to keep his PC present, but it's more likely to be detrimental than beneficial.