Not if Disney has something to say about it.
I think the Kirby heirs deserve a piece of the pie. Maybe not complete ownership of the characters, who -- to be fair -- weren't created by them and have been considerably changed over the years. But a piece. A continuing royalty in perpetuity. Not even necessarily any control over use. But every time one of Jack's characters is used, they should get a percentage.
Re: Spidey. Both Jack and Joe Simon have always claimed that they came up with Spider-Man. Stan says it's not true. There's evidence on both sides, and since most of the people involved are dead, we'll likely never know. A lot of it comes down to how honest you think Stan is.
I Agree with this. At this point any kind of ownership transfers would have serious damaging effects on the properties even if only half ownership because it would become a constant fight over usage.
The Heirs getting a piece of the pie each time characters used would be sufficient