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.
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.
I haven't heard any news about Hajime Isayama creating another manga. Usually, such announcements would come through official channels or reliable sources, and there haven't been any of those yet.