That depends on how he loses.
First, just to get it out of the way, Silva gets an instant rematch because he was the almost completely dominant champ for years, and so many believe his goofing off was a big factor in his loss.
If Silva walks in and smashes Weidman, then no instant rematch for Chris. If he plays with him and then finishes him off in the first two rounds, then no instant rematch for Chris.
If it's a close fight, and especially if it's a war for five rounds and/or a controversial ending, then yes he gets one.
"I don't deserve title shots, titles shots deserve me." - Chael Sonnen.
Just because you see the lions teeth, it doesn't mean he's smiling.