I HIGHLY doubt that Apple will start shipping 19" iMacs at MWNY or even MWSF '03. It's just way too soon, and it would also make the look of the iMac be very weird, even if it wasn't top-heavy.
I can believe 17" iMacs at even MWSF, but not 19" ones. I would love to be proved wrong, though. If there was a 19" iMac, I would rush out and buy one.