He isn't going to say there existed collusion, he was never appointed to find collusion, besides, collusion isn't even a crime
What Mueller could uncover is coordination between the Russians and the Trump campaign. Given the individuals running the Trump campaign, I'm sure they did work together, not as an orchestrated effort though, but because they were so naive and stupid to realize it isn't allowed
And what is going to be devastating is when Americans are shown the unethical and shady characters that dominate Trump's world, if you think Benghazi fed six years of Clinton innuendos get ready, we're going to see the same if not more for the next two plus years with Trump. It will almost guarantee him bumping Harding up in the ratings