Orks see a forest, nothing to fight? move on...
Orks see a military depot, nothing to fight? loot it...
Orks see a hamlet, nothing to fight ( or cant fight back

) move on...
Orks see a day-care center, nothing to fight? move on...
I see the galaxy of w40k as a sort of organism, with the Tyranids being the germs.
The Space Marines those overpriced pills that come in different fruity colors and flavors (yummy!
The Eldar and Orks as your immune system
The Necrons the cancer you got from eating too much BBQ
The Chaos and Deldar the gakky lungs and bloated heart you have from too much Space Marine, and Eldar Immunodeficiency.
The Imperial Guard those cheap and inexpensive tablets and cough syrup
The Tau being those "supposed" chinese/japanese miracle cures and whitening soaps
The Sisters of Battle your old mommas hot chicken soup cure (add some malungay for better effects, it works i promise!

)
In the end it really depends on how these races adapt to the new threat of da nids...any one agree with me on this? (
id like your opinionz so i can become a better ork

)