so based on speculation i'm seeing, season 2 could be announced in January and could start airing in April. I don't think Dr. Stone will be one of these series with such large breaks.
Demon Slayer and My Hero Academia are two with really long breaks, MHA because the anime very nearly caught up with the manga before they had a huge hiatus. One Punch Man also doesn't have enough material for the anime to adapt and the animation is hugely time consuming. Jojo takes about 8 months or so to announce a new season, and then 2-3 months to come out so about a year.