Should be interesting to see what they give us for classes. That's a big thing that I find directly gives each edition its feel.
I would rather they drop PrCs. If kept, then they'd be a 5 levels type class. The class tree idea, like in SWSE, could be neat. Yes within a month there will be 1000 new tree classes out there thanks to Dragon online and D20 publishers.
Which classes would I like to see. I have to ask that to myself. Not sure really. Not yet.
I would like more archtype feel. Monk and Bard would be a type of traveler class. Not from around here type of deal. Not the anime warrior and lute playing idiot.
I like the idea of cleric over priest. Paladin its own class, though I'd like a return to its roots. Let the cleric be the holy warrior, crusader, the adventuring priest (Friar Tuck), holy mage and prophet (Moses) again. Paladin is a hero. And in medieval fantasy, that means a knight. I think I'd like to see a paladin be built more for fighting the big monsters, like dragons, devils, liches. I've never been a druid guy. But I would expect lots of people being upset to see it become a tree class of cleric.
Keep barbarian, fighter, ranger, rogue (or thief even). I do miss the assassin. Keep wizard and call it wizard. It would be a perfect class for specialist wizards. I would like to see them DO AWAY with the 8 schools and just have "x" number of tree for all the popular archtypes, like an enchanter (beguiler), necromancer, warlock. Not sure why a sorcerer might be needed if they update the magic system, but I suppose one of the two arcane would have tougher magic while the other has many more lesser magics.
I like the marshal from MHB. Add me in hoping the warlord is the next generation of it.