No, they won't get much bigger. I'd pick the largest side shoot. That one looks just about right. The smaller ones might grow a little bit more without unfurling -- depends on the temperature and soil moisture levels.
If you want to succession plant, it's probably a good idea to "pull" them now -- harvest the little side shoots as well as the tender leaves to use like kale. Basic formula is to sow/plant the fall crop by 90 days before the first average fall frost. Actual last day to plant would depend on the variety and days to maturity (+14 days for the "fall factor"). But broccoli can take light frost and you can also protect them with floating covers.
I say "pull" in quotes because I cut them off at ground level, apply compost to the bed, and sow/plant next crop off to the side. This way, the roots break down in the depths of the soil as organic matter.