Now Valve writer Chet Faliszek says the L4D1 DLC coming in September, dubbed Crash Course, was originally intended to be released prior to E3 and Left 4 Dead 2's announcement.
"I think in this case we just didn't message correctly," said Faliszek to Offworld. "We didn't make it clear that Left 4 Dead was still going to be updated. We just didn't think to mention it, we were focusing on other stuff."
"We, internally, always knew we were going to do cool new stuff, so we didn't say anything about the original game," he added. "Of course we also intended to get the Crash Course DLC for L4D out before E3, but some things held us up."
"I think if we had that out before the Left 4 Dead 2 announcement, then it would have been clearer for our intentions. Losing the opportunity to get that right hurt us, but I think we made the right choices otherwise."

I agree with your thoughts on TF2, but I don't that immediately obligates Valve to give every title that same treatment.
Actually that's rubbish. Lombardi made quite clear that there would be more content for L4D: "Stay tuned, there's mor...
well they said it would be there, then they announced 2, and people made the assumption that meant no content for 1. ...