Because of the finding of the German archaeologists, we can now confidently say that the “open air temple” theory is invalid and that the architects of the Segesta Temple did in fact intend to build a temple that would, eventually, have a cella, a roof and all of the other customary features of a Greek temple. But they never got around to its completion. So the fact remains that the Temple at Segesta was never finished.
The plan on the slide shows what the finished temple might have looked like.