In most major markets yes DirecTv does offer the "main" HD local feed from the big 4 networks ABC NBC CBS and FOX. What DTV does not currently offer, (as is why you need a OTA antenna if you want to watch them) is the various digital subchannels that are broadcast. whether they are HD or not. Not everything that is being broadcast digital is HD.
Like Cincinnati, say WLWT channel 5. They broadcast a digital signal, OTA, that consists of the primary channel, 5-1, and a subchannel, 5-2, which happens to be their 24 hour weather station. The old analog is just channel 5. No dash, or anything. DirecTv only retransmits the primary channel. As far as I know they have no plans to include the various subchannels.
Lot of people get confused by this when they hear about the 2009 cut-off. They think they have to have an HDTV set. Or that their current DTV box, if it is standard-def, will be turned off. IMO the FCC and the major providers have done a piss poor job of informing the public about what is actually being turned off. or what the whole 2009 thing is all about.