I think it's a safe bet that they WILL develop them -- if they don't, then they're basically giving up on all future Mac printer sales. That seems like a reasonably good sized chunk of business to just throw away.
A more interesting question is when they'll develop them. My money's on July-ish, when OS X comes pre-loaded with new Macs. Since there are often bundle deals that include Epson printers, I think they'd want to make sure that the printers work by then. But I don't see much incentive for them to hit March 24th, unfortunately.
I hope I'm wrong and that Apple's thrown as much money and resource at them as necessary to insure we have drivers on March 24th .