Potty Training

My 2.5 year old son has absolutely no interest in potty training. I’ve done stickers, prizes, bringing him with me, putting him in undies and making him sit every 20 minutes. Nothing has worked. I’m guessing he’s just not ready but I feel like I need to get it done before Preschool in the fall. Maybe summer will be easier because he’ll be in swim pants all the time? I don’t know. He just pees in his undies when he has them on, or pees on the floor if we do pantless days. Do i keep trying or wait for him to be ready???