The GTAV trailer recreated in GTAIV then thrown together side by side.
Looks like the core tech in V is the same as IV but there's small refinements everywhere giving it a much more crisp, sharp look. Textures and Lighting look like to be the biggest improvements at the moment. The tech also looks a lot more solid with the small graphical glitches seen in IV not showing up in V.
So here's hoping for no Quincunx AA and a proper HD resolution!
And no it's not Tommy Vercetti...
Mucho thanks to Beanmike206 and Nowgamer for the videos.