lower resolution, lower frame rate, reduced anti-aliasing or effects, yeah, all of those seem likely. you have to assume devs will take advantage of the added power and just hard code lower settings so that things work on PS4. that seems to be a best case. worst case you get things that actually run horrible on the launch console.
it will be interesting to see how the market reacts to consoles going with a phone/tablet like refresh cycle. i just don't have as much interest, i am very ambivalent about the current crop of consoles. i'm no longer in the target audience though.