The older characters such as Kakashi would be cautious. They would recognize Naruto but also be worried about the implications of someone from the future being in the present. They would want to know if his presence could change the future in a negative way. For example, they might fear that his actions could lead to the earlier awakening of a powerful enemy. As for the villains, they might see future Naruto as a threat and try to eliminate him as soon as possible. Orochimaru, for instance, would be very interested in Naruto's future powers and might try to capture him to study. And the new generation of ninja in the past would look up to future Naruto, seeing him as a symbol of what they could become.
At the moment, there's no definite information about more Dr Stone manga. It could happen if there's enough demand and the creative team is up for it. We'll just have to wait and see.
It's hard to say for sure. The decision often depends on various factors like the popularity and sales of the original series, as well as the author's plans and the publisher's strategy.