We know that there are 'rules' between Widmore & Linus, but it is not clear how these operate. We also know that both Widmore and Linus think that separately they are acting in the island's best interests; however there is a great deal of enmity between them. Linus & Widmore are playing out a script (almost literally) which will have them replicate the roles of Jacob/MiB which are played out at a higher Level. Linus, in killing Jacob, has come to a new understanding of the island, and has gained in humanity. He is now best suited for the Role of Jacob; Widmore is obsessed with protecting the island, the role of MiB. That is his destiny. In essence, Linus/Widmore = Jacob/MiB becomes a self-fulfilling prophesy, with pre-echoes over the past 50 years. Linus will come to understand Alex's death in all this, and accept that it was part of his growing, and part of the process leading him towards being the new Jacob, a role which requires compassion, understanding, but also ruthlessness. Widmore would never understand such subtleties; he is a bully and a brute, completely direct. His destiny is to kill MiB, just as Ben Killed Jacob. When that act is executed, the cycle will be complete, and Ben/Widmore will be transported back to beach at the start.
Widmore: "Do you actually know how much I want to kill you, boy?"
Linus: "...and just how did that work out for everyone before?"
Widmore:"One day, I'm gonna find a loophole"
Linus: "Well, when you do, I'm sure you'll let me know."
My questions are: Was Jacob actually Ben? Did he kill himself? Does MiB recognise Widmore as an earlier version of himself, and is he trying to circumvent what he knows is going to happen, but in fact is powerless to prevent it?