do i need to create new characters for this new season what do i do with all my old season ones?
Whatever you want. You can rebirth them into the new season, or just delete them if you don’t play non-season.
I create a new seasonal character, then delete it when season ends, after I transfer any useful items to my non-seasonal characters.
As TimberWolf stated, you can create a new Seasonal Character or Rebirth one of your non-Season Characters.
I have one “placeholder” Character each, on Normal non-Season and Hardcore non-Season. They have both completed Campaign Mode in non-Season and keep me from losing my Progression. If I feel like playing D3 between Seasons, they are the ones I play.
I also have one main Character each, on Normal non-Season and Hardcore non-Season. On the last day of a Season, I salvage everything I don’t want to keep and put the rest in my Inventory. My Seasonal Stash is completely empty. That way, I don’t have to deal with items being mailed to non-Season. I strip my main Characters naked to await the start of a new Season. When a new Season starts, I Rebirth them. They reset to Level 1, but retain hours played and Lifetime Kills.
What you decide to do is your choice. If you never play non-Season, then TimberWolf’s method is probably easiest with less maintenance.