I think it depends on his inspiration and motivation. If he has a story he's passionate about, there's a chance. But it could also be that he wants to take a break or focus on other things for now.
The legality of online manga varies. Legitimate platforms that have obtained rights to distribute manga are legal. However, sites that offer pirated or unlicensed manga are definitely not legal. It's important to support legal channels to ensure creators are compensated for their work.
I don't know. Making a new manga is a big decision and involves a lot of effort and commitment. We'll just have to wait and see if Koyoharu Gotouge decides to do it.
I don't know for sure. It depends on a lot of factors, like his inspiration and personal plans. We'll just have to wait and see if he makes an official statement.