It is faster than the speed of light--which is why "expansion" is controversial.
Some physicists speculate that the speed of light has been slowing down since the Big Bang.
Um, no. Expansion is not limited by the speed of light because it's an expansion *of* space, not the speed of something traveling *through* space. Only the latter is limited to the speed of light.
Some physicists speculate that the speed of light has been slowing down since the Big Bang.
The only people I'm aware of who speculate such a thing are certain young-earth creationists who are trying think up reasons why the obvious age of the Universe doesn't actually mean that the Universe is older than 6,000 years old...