It's definitely possible.
Machida's faster, but speed doesn't always win fights. He was faster than Shogun and was still knocked out cold. Faster than Jones but still dropped and submitted. Faster than Rampage and Davis and still lost decisions.
Weidman has great timing and control of distance, along with great fundamentals and big power. The longer Machida wades on the outside, the more Weidman gets his timing down.
I wouldn't be surprised to see Machida get dropped/finished by rushing inside.
Also, Machida looked like a fish out of water when he was under Davis. If Weidman gets him down (which he could), then it's definitely going to get ugly.
BTW, to everyone touting Machida's TDD, when was the last time he fought a great wrestler at MW?