It's a really tough fight to call in my eyes. Randy is good at controlling a fight and keeping a great pace. Great wrestling, clinch work, and dirty boxing. BUT there are instances where he loses concentration and leaves openings; just look at the Liddell fights.
I think against a guy like Machida, the worst thing you can do is leave an opening. He is super accurate and can exploit openings well. On top of it Machida is amazing at maintaining distance and has a sumo background that helps his TDD.
Tough fight to call but I'm leaning 55:45 Machida via decision or tko.