It depends partly on what variety of tomato you planted. I have Super Fantastic and they're still loaded with fruit, though I think they got sunburned (at the very least) in the last couple of weeks. They are "indeterminate" so they will bear fruit all season ("determinate" has a crop and is finished.) I've managed to keep the spider mites and such under control, but there could be some kind of blight involved.
Sometimes I'll let the plants stay put, ugly limbs and all, and they put out new foliage in the fall. With large established root systems, it means I may get a good fall crop on the new foliage. If you plant new, you have smaller plants and may not get as much (but if they're free of problems, it may be on a par, so it is a judgement call.) Sometimes I cut a few branches off and let it send out new limbs. They will - depending on how and when you cut them back. You might want to experiment; trim a few, leave a few alone, and see what happens.
I do keep adding Garrett juice any time I do foliar treatment (for tobacco hornworms, for mites, for whatever) and I include a liquid fertilizer and molasses. Every so often I pour water on that has epsom salts dissolved in it. Don't treat them like they're already dead and maybe you'll get more life later. And even if you don't, the things you are adding will just keep the soil healthier for the next crop.
Not very scientific, just based upon similar experience. I hope it helps!