Hmn can' say it's among my favorite Ghibli movie but I think Porco Rosso is underrated. I think there would be a more upset outcry about a sequal to Spirited Away, Kiki, etc. I think with Porco, it could only get better being in Miyazaki's hands. I am very curious too whether it means he'll be human in this movie. I can understand Miyazaki's interest in a movie with a bigger male protagonist.
Hmnn I wouldn't mind a sequal to Howl's Moving Castle actually if he based it off of the book sequal (threequal?) House of Many Doors. New cast of main characters but still a great interaction with the old I loved the book as much of the first and kept imagining it in my head as a miyazaki movie.
I think I'll cry the day Ghibli stops making movies and I studio Ghibli disbanding would make it even worse even though it'd be hard (or impossible) to fill Miyazaki's shoes.

It's my hope they find a way to carry on when that day comes.