One of the most common headlines I see in popular science articles is "Was Einstein Wrong?". While it is certainly true that relativity is going to be replaced by some more advanced theory of physics at some stage, the basis of Einstein's theory is unlikely to change.
I really wish people would stop planting the laws of thermodynamics in their arguments as if they're an irrefutable line of defence. Thermodynamics is 19th century physics, we've moved on.
There is a split in the philosophical community with regards to this issue. By and large, the majority of philosophers of physics claim that space and time are real and important entities, but there is a small faction who maintain that space and time are just useful theoretical constructs that don't have the independent existence we sometimes attribute to them.
We can get most of the way to deriving the constancy of the speed of light just from the Principle of Relativity alone. In other words, the speed of light being constant is just a consequence of the laws of physics being the same in all inertial frames.