EX is probably being left behind as a remnant of the bygone era. The term "EX" might in fact be detrimental to sales; it MIGHT be confusing to people who confuse it with "DX", or with a lens mount. Who knows? It appears that the all-new "C", "S", and "A" markings on the round plates are now the new thing... "EX" also has a slightly negative connotation...ex-wife, ex-husband, ex-girlfriend, ex-employer...who knows...to a non-familiar buyer, the two ,letters "EX" probably do not mean much. If Sigma really wants to go in this new direction, with the Art, and Creative, and Sports lens descriptors, then the broad, overarching "EX" designation would seem superfluous. When Canon switched from the FD mount to the EOS system, they dropped the entire FD nomenclature and went to calling their lenses "EF". Minolta did the same thing with their MC (Minolta-Celtic) which went to MD mount,and then when AF came in, A-mount. I dunno...this entire idea of Creative, Art, Sports association with lenses---this is as far as I know, unprecedented.