Would I mind? I'm not confident, but I think we're going to see updated graphics. Are you really confident that GT5's graphics are going to be a carbon copy of GT4's graphics? Let's take an example from another game. People said that NCAA Football 2005 looked more like NCAA Football 2004 even though the 2005 game was more advanced in terms of play-calling, sounds, weather effects, and such. There is no such thing as "Gran Turismo 2005," "Gran Turismo 2006," and so on. So how can you tell me (or anyone else) that GT5 is going to be a mock-up of GT4 graphicwise? Think about it. New system, new capabilities, but re-used graphics. Now answer me this. Does that sound right? You'd rather TAKE ADVANTAGE of new technology and not keep things unchanged or relatively changed. Almost every successful game franchise tries to do this. Would you rather keep GT4's graphics and make a new game? Hell. PD may as well taken GT2's outdated graphics and used them in GT3 on the PS2. Tokyo R246 and the TVR Cerbera Speed 12 would have looked like somewhat modified PS1 graphics.
For this reason, I don't think this is going to happen, I'm more than 90% sure of that. I would like PD to take advantage of the PS3's power and capabilities as best as possible. That's how you make the good games, and every franchise from Mario to Metal Gear Solid to even Halo do this. What's the point of showing off the PS3's capabilities using age-old graphics? Take advantage of them as much as you can no matter what. Damn it to freaking hell, you're in competition against other racing games in class (namely, Forza Motorsport). While GT4 was lovely, GT5 should surpass our imaginations from graphics to gameplay.
So my choice to "should GT5 feature GT4's graphics" isn't listed. Because my answer would be hell f:censored: no!!! Go ahead, PD. Make the graphics at least 25% better than the beautiful ones from GT4. Take advantage of the new engine, make dynamic tweaks such as changing weather and time cycles. Who'd want a redone GT4 as GT5? So no. Make everything better than the last.