Crossrail ensures that LHR connects more people to the City faster, relax, LCY going away would not be the end of the world
It is not about getting to/from LHR faster, it is about getting
through LHR faster. And Crossrail will not change that. As the behemoth it is, LHR will always be a major pain to pass through. I avoid it like the plague when travelling to/from LON proper and have only started using it again for connections since T5.