Your summer workouts depend on if you are going to competing during the summer. If you are competing, how many events do you wish to perform at your max. potential, etc.
If you are not competing then it is easy. You work on your base, that means miles, I am not talking about distance miles of 40+ per week, but 20-25. All elite sprinters do their base work after the World Championships into the indoor season usually until their 3rd or 4th race. They keep their speed sharp by doing speed work 1-3 times every two weeks. A sprinter should be able to comfortably finish a 5k race in 21 minutes, a 400m specialist should be looking at something that is around 6:00 per mile +/- 15 seconds, their training should be around 8:00 pace, and do intervals 10×400 at 15-20 secs off 400m race pace or 15×200 at 32-37 secs. Also, if you are a 400 meter runner you have a tough choice to make in the fall if in High School, between Cross Country and Football, from personal experience Cross Country will make you a better 400 runner than Football will.
Two things I can guarantee you if you train like I said is that the 200m and 300m intervals and repeats will not hurt as bad next season and 400m+ work won’t suck as bad, but the speed work will be a piece of cake. You’ll notice the difference.
Another thing that helps during track season is getting outside your event every once and a while, ie open 2’s and 8’s and 4×2 and 4×8 relays.