I actually think it will be mid/late next year before you get to see any real differences, just because of the amount of effort required to make games on so many platforms. I mean Assassins Creed is coming out on about 6 different platforms, when you do that, you wont be spending much time on enhancing the performance of particular platforms, as they wont have time.
Games coming out this year will have some advantages over their current gen machines, but it's probably a mad rush to get them to work correctly and out on time, so there will most likely be problems with games on both PS4/XboxOne.
So i wont be expecting any major differences this year to be honest... it will be 1st party games that will hold the initial key to performance over the next 6-8 months.
Also Driveclub was very much a concern, i mean they even stated the game was only 35% complete, with only 4 or 5 months to go, thats hardly any time at all.