The update is supposed to be huge and there are lots of things that have to all work together so probably a little of a, b, and c and probably the occasional e.
Red is very detail oriented and likes to make things as close to perfect as he can. Any outstanding bugs are not game breakers. He stomps those quickly. This update is supposed to replace player models, most of the game tools and weapons, crafting stations too from what I hear, and add lots of new stuff (ranged weapons for one). This will open the door to NPCs and monsterd and who knows what else. So much of the new modeled items I hear were designed with new animations for the new player models so they would not look very good with the current ones (Red likes his updates to be polished) which are kinda becoming an eyesore considering how nicer the newer crafting stations look. I think the goal was to eventually replace all the old modeled stuff with better looking stuff. So goodbye pizza oven smelter? Who knows.
BTW I'm suspecting that this is going to turn into a two or three part update (kinda like the dungeons). I've been told that most likely rideable horses and camels will not be in the first update. The NPCs ( merchants, raiders, hermits, and such) will no doubt follow this first one.
The E3 is over now, right? It would have made sense to leak something ahead of that but I suppose that if he missed that opportunity that there the upcoming Steam Summer sale. It certainly would be a perfect opportunity now especially considering how dated the trailer is beginning to look.
Gotta be patient. The team is small but the workmanship is excellent. BTW, Red51 is a he (atleast I havent learned otherwise).