Don't forget that the taste for Greek art came not only from Syracuse, but all over the Greek world during the long conquest of it (from the conquest of the southern Italian cities to Sullas campaigns in the east).
Changes in architecture and art are already in motion, slowly, by this time. Consider that some even argue that Roman history should end with Marcus Aurelius (Even if I believe that is very premature), others say Alexander Severus (while some say Diocletianus, Constantine, Romulus Augustus etc). Anyway my point is that this is a period that tend to spark thoughts of change towards the middle ages and byzantine period. I'm not trying to say that the baths of Caracalla were byzantine in style when first constructed, but they may very well have been moving in that direction so to speak.