AoE would be very nice. Honestly, in gameplay, it's the one glaring weak point that I can really feel in PLD versus other tanks. Just about every other job out there (with the exception of maybe MNK?) has at least the ability to do some pretty solid burst AoE damage, while sustainable AoE is a of a niche. PLD's block mechanic is built for situations where they'd be taking a lot of hits - it's where their mitigation model really shines. And yet, the PLD enmity mechanics and gameplay mechanics give PLD the weakest AoE in the game, with its only damaging move being locked to a lengthy cooldown. Paladin is built for AoE tanking mitigation, but single target enmity generation. It's kind of backwards.
I'd like to see some way for PLD to do more AoE damage. We have a couple of DoTs (CoS and GB); why not make it so Flash spreads and/or extends/refreshes them? Have Flash pass around the Goring Blade DoT to up to two additional enemies, and have it extend the duration of the CoS DoT on all affected targets by 2GCD/6 seconds.
I also hope that they aren't adding more skills/abilities in 4.0, and instead take the traits route to alter how various abilities behave and interact.
I'd rather they adjust the combat table to make the two rolls independent, so that it is possible to both block and parry an incoming hit (call it a critical block or something). That, and parry needs to be made more useful anyway. Even if they just moved the parry roll ahead of the Crit roll, it would suddenly become desirable for PLD again.