I don't know why this hasn't really been posted anywhere else. But alas.
Technology channel G4 TV is due to host a televised showing of GTA IV's gameplay on their channel at 12:00 PM EST noon on Sunday, April 27.
This is really the only official (and definite) video before launch, and considering it's "commercial-free", I expect it to be at least 30 minutes long. G4 has also stated that an array of gameplay videos will also be up on their site at noon Sunday, also. So keep your eyes peeled/refesh button close.
How's that for a gameplay video for you guys?