I also don't think there will be a card swap, Aggro is good but not OP. What Duels probably wants for this is some good removal for artifacts that is not Sideboard material - think
Putrefy or similar effects (which any colour but Blue has gotten btw).
Tezzeret will be a great addition to the slower artifact decks Nighthawk mentioned; him plus 2 or 3 other cards might be what pushes these decks over the Edge for Duels and maybe for Standard as well.
I hope there will be more Energy payoffs cards; that is the theme needing the most help. So far, the bombs there are too expensive/slow, and the Aggro deck is not quite consistent enough, making Energy more of a side-note mechanic than a build-around.
With Selesniya being maybe my favourite guild, I can't help but look forward to Ajani. Currently Selesniya needs a push, Ajani might be just that.
Regarding Vehicles, there is hardly any room for better ones than we have already I think. Cruiser and especially Copter have set the bar for new Vehicles to be good very high - and it's really hard to get close to that bar without being a broken card.
Maybe we'll see a couple more good Dwarves that would make the cut in these decks, but even there the bar is high looking at Veteran Motorist and Depala.
I hope Black gets some help, but I think it will get some for Tezzeret alone. It might not be the kind of help needed for something like Esper Control, but it could very well be the help an artifact-based strategy in Grixis or Esper needs.