My interpretation of the ending:
Desmond and Lucy, along with the 2 other characters find the apple of eden (in the real world). Desmond takes hold of the apple, and suddenly is taken over by some force, which forces Desmond to stab lucy in the stomach. When this happens, the game ends, credits begin to roll. If you watched all the credits, you will have heard the voices towards the end of the credits saying "We need to put him back in the animus" while another voice says "Why should we put him back in the animus when it was what destroyed him in the first place". This is obvious evidence that there will be yet another sequel which is totally fine with me.
What information was given in the ending if any?
Why did Desmond or whoever was controlling Desmond when he had the Apple of Eden in his hand, decide to stab Lucy.
Where the people talking at the end of the credits templars??