Well I thought just the same thing lol
I think we should all wait for the Beta to come out, so that we can see testers' feedback. Since Eden practically said they'll choose people with all kinds of rigs, I'm sure there will be at least one person running the beta with min. specs and recommended specs. If the game runs poorly even on great rigs, I'm sure we'll see all kinds of posts in the official forums :D
I'm hoping people with 8800s and HD3870s will be able to play the game fine, without lowering all details and resolution. If I was waiting for TDU2 to update my PC and really had to, I'd either get a HD5770 or, if I had the money, a GTX470 or a HD5850/HD5870. If I had at least a GTX260/HD4870 or greater, I'd wait till I get some feedback.
Since perhaps the Beta is almost out, we might get these answers real soon :D (at least I hope so lol)