I just cut back our Celebrity tomatoes, a determinate variety, to get a second crop in the fall. Determinates are supposed to set fruit pretty much all at once, then they are finished.
One year I didn't get my fall tomatoes started, so as a "desperation measure" I cut back our existing Celebrities, just on the off chance we might get a few tomatoes. The Celebrities grew, set blossoms and fruit, and we had a lovely fall crop from the same plants we had harvested from in the spring. We've done this for several years now, and if the drought lifts, we may get fall tomatoes again this year.
If you have the space, and your frost date is still far enough away, you may want to try this with a determinate variety and see what happens in your garden.