Ok, so now that wizards spoiled the spoiler I'm going to give my opinion on what are cards to look out for and hope we get/don't get, Depending on what you like to play/don't like to play against:
White (got plenty of love, especially Humans)
Collective effort (plenty of value: removal, Enchantment hate and big nissa's -2 pump? Crazy...all for 3cmc)
Deploy the Gatewatch (ramp power Rangers drops this and suddenly 2 or 3 of them appear from out of nowhere... Ouch. Won't be that widespread but I bet a successful use of this would make me rage quit)
Long road home (blink that saves a creature from sweepers or removal, exploit etb and pumps? For 2cmc??)
Repel the abominable ( selective fog, protects from damage based sweepers/removal, 2cmc and Uncommon. Lots of utility)
Selfless spirit (this guy is going to be everywhere. Cheap evasive flyer spirit that is splashable and nullifies half the sweepers? At least it forces your opponent to kill it before they can sweep...)
Sigarda's aid (awesome effect. If this become popular, auras may become a thing. Equipments are kind oh meh right now. Problem is when it doesn't show up if you build a deck around it)
Thalia, heretic cathar (totally broken... Try using that new Ball Lightning with this on the board... Forget haste, forget non-tap lands)
Thalia's lancers (beefy body on a legend tutor? First Strike is gravy. 5cmc is high, but worth it. How many legendas are among the best cards in the pool?)
blue (some interesting stuff)
Contingency plan (delirium in one card + scry effect. If its not totally bugged, in the right deck this is awesome)
Displace (another blank effect. As if there weren't enough already. This time a 2 for 1... 3cmc is the worst bit)
Imprisoned in the moon (this is the best blue card from the set and its an aura... Only PW hate too...)
Lunar force ( I don't care what the nay sayers say. You'll see why its annoying after the update hits)
Mausoleum wanderer (spirit Tribal's best 1 drop. Can completely throw off a distracted opponent)
Nebelgast Herald (counter Spirits could really become a thing... Spirits is probably the best Tribal after Humans.)
Scour the Laboratory (overpriced ancestral really? Yes please! This is why you play Lunar force and want delirium. At least they didn't Ruin it by making it Sorcery)
Spontaneous Mutation (Instant speed aura to nulify a creature's power? Cheap too. More effective later on, good in a delirium deck. Interesting)
Summary Dismissal (the mother of all counters. It counters everything and sounds too hard to code. If they couldn't make Emrakul, they can't do this either. But, its definitely good...)
Take Inventory ( I want, I want, I want! This promises to be really good, what a shame its not Instant... Brain in a jar it anyone?)
Black (probably the weakest color...again. Did get a couple of good cards, a lot of zombie Tribal but nowhere as good as human or spirit)
Cryptbreaker (very good, much needed zombie Tribal 1 drop. Makes Tokens, enables madness and delirium and can draw cards...)
Dark Salvation (big token generativa and removal. Looks decent)
Liliana, the Last Hope ( lilly has already been discussed. Cheap, ok Walker with zombie Tribal synergy)
Murder (Instant, unconditional removal. Black's best card. Double B will Hurt it as a splash, but that hasn't stomped people playing Grasp...)
Succumb to Temptation ( Instant read the bones. Double B, same problem as Murder)
Red ( some new toys, Tribal vampires and werewolves is mostly meh, but a few good playable cards there)
Bedlam Reveler (I have a deck just waiting for this guy... Much needed Red draw)
Borrowed Hostility ( this card gives you options. Its Titan's Strength +3 damage on a non-blocked attacker or first Strike on a blocked one, saving it from a trade...or both at an overpriced cost)
Collective Defiance (just awesome, every option is good. Gonna be cast for 5 cmc alot)
Deranged Whelp ( 2/1 Menace? Another good 2 drop for RDW. Evasion makes it look very good, better than Glory seeker...)
Galvanic Bombardment (already been discussed. Fiery Temper substitute)
Impetuous Devils (slightly more expensive Ball Lightning with a perk. Careful with first Strike... I like It)
Incendiary Flow (why isn't this Instant? Still, 2cmc for 3 damage that goes to face is nothing to scoff at.)
Mirrorwing Dragon (finally a playable Dragon in duels. Painful to kill curve topper)
Shreds of Sanity (Red Now has a way to cast 3 Exquisite Firecrafts. Be warned)
Stromkirk Occultist (this one I'll have to test. Looks playable in theory...)
Thermo-Alchemist (I've been itching to make a Ping deck with Nettle drone but this is better. Should live longer and is cheaper)
Green (not that much good-stuff, maybe slightly better than Black)
Clear Shot (more expensive +1/+1 rabid bite. Green removal is not exactly abundant... Still need to have a creature)
Eldritch Evolution (this creature tutor is going to be played a lot. Tutor for Bellower and get an advocate while your at it... Careful with counterspells...)
Gnarlwood Dryad (good 1 drop,, gets better with delirium)
Hamlet Captain (human Tribal... As if Consul's Lieutenant wasn't bad enough...)
Permeating Mass (such a deliciously fun card...)
Spirit of the Hunt (Wolf Tribal, flash 3/3. Pretty good ar 3cmc)
I'll do multi-colored, colorless, flip and meld tomorrow. Bare in mind, these are my opinions and you are free to disagree with me.