It probably wouldn't matter if there were an O-Ring burn through on Ares I, as the fuel tank on that one (for the upper stage in this case) will be up on top of the SRB, not next to it. A burn through could screw up the trajectory, but shouldn't cause an explosion on Ares I.
On Ares V, if I get this right, it will look like the Shuttle tank with two SRBs attached directly to it as on the current Shuttle stack, but the rest of the stack goes on top as well. There are also liquid fuel engines beneath the tank. Frankly it will look much more like Russia's Energia or France's Ariane 5 when it's all up.
Ares I and Ares V
Energia vertical stack configuration:
Or the French Ariane 5:
There is no external tank to be breached and detonated on a vertical stack approach.
And the O-rings were fixed after Challenger. And even now, just to be extra-safe for the shuttle, they launch only in warm days so the material is at its most effective to seal...