The "biggest ever update" for Gears of War 4 is slated to arrive on June 6. The "Rise of the Horde" update for the game will be free to everyone and will add in 15 new skills, level 6 skills, two new difficulty levels, and 20 new achievements.
NEW SKILLS
Both the new and existing Skills can now be taken to Level 6, making them even stronger than ever before! The new 15 skills arriving in Rise of the Horde focus on providing new ways to specialize the way you play your Class.

Engineer
Flow – Take reduced damage while repairing fortifications
Overclock – Increase the rate which Weapon Lockers replenish ammo
Salvage – Enemies killed by your sentries have a chance of dropping ammo magazines

Heavy
Thick Skin – Take reduced damage from explosions
Berserker – While carrying a heavy weapon you deal more damage as your health gets lower
Last Stand – While carrying a heavy weapon you take less damage as your health gets lower

Scout
Dodge – Take reduced damage while roadie running
Speed Loader – Roadie running will reload your equipped weapon automatically with Active Reload rounds
Cloak – Being stationary and in cover for seconds will cloak you from enemies – leaving the cover or shooting will remove the cloak. Shoot enemies from Cloak for a small damage boost.

Sniper
Steady Hand – Take less damage and have reduced camera shake (when being attacked) while aiming or scoping
Magic Bullet – Critical hits with precision rifles (Longshot, Markza, EMBAR) penetrate through enemies and increase the damage of the next shot
Called Shot – Targets you mark take increased damage from all sources

Soldier
Siphon – Planted grenade kills cause enemies to drop more Power
Resupply – Regenerates one grenade every [X] seconds (up to starting loadout number)
Assault Rifle Accuracy – Assault Rifles become more accurate the longer they are fired while in cover

BOSS LOOT DROPS AND MORE
Take those new Skills out into the field and defeat Bosses in Horde Matchmaking for new rewards – each Boss Wave you defeat at Wave 30, 40 and 50 will drop a singular random Horde Skill. Harder difficulties increase the likelihood of a rare drop, so challenge yourself for the best chance at an awesome drop.

We've also now added a new UI feature that now shows how many Power drops - and how much they are worth - are left on the field. While this benefits the whole team, Scouts can now rest safely at the end of the round knowing they cleaned up every possible Power drop out going into the next Wave.

These were just some of the details on the new skills. I didn't even show off the new difficulty levels, the new maps, the new achievements, new card packs, ranked crossplay, additional rewards for new players, or even touch upon how they're offering up a free trial of the game to everyone. For the full details and the full changelog, hit up the Gears of War website.