first thing first : Gears Of War 3 is not going to be last sequel for this franchise .
the game will apparently start one year or so after the events of Gears Of War 2 . the humans are now positioned in several large camps around the world . now the coalition of organized governments has more time to examine their enemy . the Locusts , they have ruined men’s lives , brought nothing but misery and sorrow …….. but they have to be something …. They are neither ghosts nor Aliens !!! . they have not reached the earth via UFOs and they do not carry laser guns . Locusts are of this earth , they live in underground , they carry human weapons , they talk in human language , .................................................................they once were human themselves !!!!!
Locusts are mutated Humans , they are not zombies , they are intelligent and they plan every part of their actions . they have been tortured and turned into their current form under Queen's order . the queen is an ambitious human who wants to conquer the world and therefore decides to create an army of mutated Human , an army with stronger and more reckless soldiers . Adam Fenix is an skilled scientist who decides to save mankind from the queen's ill fated desire . as you hear in the start of Gears Of War 2 the queen says : everything started with the desire for power .
Adam Fenix starts working for queen in Locust 's project in an attempt to stop her from ruining the earth . Queen herself is not aware of this and think Adam really wants to help her . Adam Fenix is alive and is still working for the queen , after significant amount of researches , Adam understand that Locusts are extremely vulnerable against a specific yellowish substance Aka Imulsion Gas . he then figure that by injecting very little amount of that substance into Locusts Body , they become much stronger , more accurate and more deadly . also after death ; these creatures can transfer their power to another Locust of their kind by means of the Imulsion substance . so even when a member of their squad dies , its power transfer to the other locusts and make them even stronger (do you remember the Cut scene in which the new locust jump towards Cole and then Cole respond with a shotgun in face !!!! the inner substance were later transferred to another glowing Dude ) , this transformation continues and the more squad members die the stronger the other members become till the last member who becomes a mobile explosive who can due a severe damage by exploding itself . so the new Generation of locusts are much stronger than the old one . also have you noticed that we can only see the new generation of Locusts only under the ground . yes , this generation of Locusts can not reach the surface as long as they want to stay alive . there is a difference between the new Generation of Locusts and the exploding wretches of the first game .as opposed to the new Generation of Locusts those exploding wretches were totally overdosed and therefore dangerous for their own kind . so a person turned the Locusts into a new form that only exists under the surface so he can use them as an army against the typical Locusts . that person is Adam Fenix . he is with the queen but literally Adam is against her .
by sinking Jacinto his plan is not functionable anymore since the flood also killed a great portion (if not all ) of the new generation of Locusts . that is why we hear Adam at the end of the credit shouting what have you done ?
so the Locusts will be back .summarize : I believe Gears Of War 3 will focus on Adam Fenix, his past , his relationship with Marcus and the Queen and his attempts to stop the Queen .