There are two reining factors in the belief that the speed of light is an absolute: 1) the state of physics and what we know/understand about friction, gravity and the way that light travels, and 2) the ability to detect and measure anything faster.
Without knowing specifically what they are seeking to measure, it is difficult for physicists to try to detect (much less develop) an instrument that can measure something travelling at greater than the speed of light.
The speed of light is the current state of technology. As soon as we discover dilithium crystals and develop warp engines, the speed of light will be relegated to travel in the slow lane!
(Ok, I’m having a little fun and made that last paragraph up!)
Who needs dilithium crystals? If you've ever seen the show Cops!, it appears that meth crystals send people beyond the speed of light...