First off, so y'all know of what I speak:
http://www.fantasyflightgames.com/edge_news.asp?eidn=4645
Now that you've read that...
Wow.
With the Z-95 Headhunter, we have something that equals an Academy Pilot's cost, which can theoretically be a 6 ship swarm for the Rebels, with 6 missiles (2 Concussions and 4 Assaults = 100 points)! Rebels are now the kings of the Alpha-Strike, and may yet be the kings of the Swarm.
It's essentially an A-Wing with 1 fewer attack die, for +1 PS and -5 points. Like the A-Wing, it dies to a Direct Hit from a Proton Bomb, which will certainly see significantly more play.
With the E-Wing, we have a third ship that dies to that Direct Hit from a Proton Bomb, and this one is terrifying in its own way. It is slightly more survivable than the Tie Advanced (previously the most survivable small-based ship in the game), has a Sensors Slot and a natural Barrel Roll (making it as hypermobile as a B-Wing), 3 attack dice, and a freakin' Astromech slot.
It has 3 native shields, can take R2-D2, and be as much of a knife-fighter as Ibtisam. It is an excellent thing it's so bloody expensive, 'cause 4 of these suckers would be a nightmare.
As for Etahn A'Baht's pilot ability, it gives all of your ships Winged Gundark's pilot ability if they happen to be shooting at someone in your firing arc, except they don't have to be in Range 1 of the victim. He's gonna be Ten Nunb's best friend.
With the Tie Defender, we have a small-based ship with 3 attack, 3 evade, 3 hull, and 3 shield: a full Hull Upgrade better than the E-Wing. It also has a missile slot and a freakin' cannon slot. Because it wasn't good enough before the cannon addition, evidently. Also, it comes with a never-before seen maneuver.
Given that we currently have a 0 stop, and a 1(Tetran Cowall),2,3,4,and 5 koiogran, my money's either on doing a Koiogran off of a bank or turn template, a 0 koiogran, or a maneuver that goes backwards. Otherwise, they'll have to release new templates!
With the Tie Phantom, we see our first ship with 4 native attack dice, if the graphic they spoilered is legit. It will also come with a Systems slot and a Crew slot, meaning it can take Fire Control Systems + Gunner.
As far as spoiled upgrades:
We now have a 3 point missile that causes a 2x Ion effect (and 1 damage). It is the only Ion-based weapon to knock out a Large-base ship on one hit, but it's also a significant 3 point missile, which will also be viable on A-Wings. 5 prototypes with Ion Pulse Missiles might be something to watch for.
We have a 3 point astromech that you activate for a conditional Target Lock + Boost, and it doesn't appear to need an Engine Upgrade on board to use it. I do not know on whom this is best suited, but it's slightly terrifying to me already.
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Overall, Wave 4 seems specifically designed to screw over everything we already know about the Metagame of X-Wing, and I am thoroughly excited to see what else we can glean from it!
Also, be prepared to spend ALL the money for this wave. Those Headhunters come one in a package, as opposed to the 2-for-1 discount that Ties got in the Core Set.