Blix and Kay say this doesn't count.
"Two former weapons inspectors — Hans Blix and David Kay — said the shell was likely a stray weapon that had been scavenged by militants and did not signify that Iraq had large stockpiles of such weapons. "
http://news.yahoo.com/news?tmpl=story&cid=540&u=/ap/20040517/ap_on_re_mi_ea/iraq_sarin_10&printer=1
Who knows at this point? How many times has the media screwed up on these stories in the short run? From what I understand there are dumps of artilery shells and ordinance all over Iraq. The guys that scavanged these shells may not have even been aware that they were chem shells. Most likely a good bet to wait and see instead of jumping on every "new development" by the second. Within a few days the facts should be clearer. For example- tests will show how old the sarin is (if it is indeed even sarin) and when the shells were made.