Hi Mark - they are fairly crowded there in that box and that makes them spindly-stemmed- assuming they are getting enough sun that is. Cauls need at least 10-12" separation and good stem support to form good heads. Those stems won't be able to support a head although you could try mounding up the soil around them to help.

So I'd have to day say no, the odds of them developing a head of any size at this point is fairly slim.

Plus, though you don't say where you are located, it is getting awfully late and overly warm for good heading unless you are way, way north. They just tend to bolt when it gets hot.

Dave

Concur; There are several purple headed varieties with varying DTM, but any cauliflower seeded in April should have a large, robust plant by now. They are relatively large plants that take a bit of room.