No. If they wiped out the previous life (wich is a hardly-believable theory, we should stay on what we know), and they can crate life, what was the previous life?
And how could they have never expected to be rebelled against?
Why should they keep the Mantle, when they exterminated their creators/creations? The Forerunner too rebelled against their creators, like the Precursors did, so why aren't they capable of keeping the Mantle?
Take a look at Director's posts.
Why did the Forerunners rebelled?
Why did the Precursors crated them? Why should they leave the galaxy?
Why did they created the Flood? If it was a test, why not another humanoid race? Why a parasite?
As you can see, there are many questions that, though they may have a fan-made theory, have no final answer.