@LGS6753
It depends on what you mean by 'substantially'. There was an outline plan to add an extra track for a critical stretch in North London of the London Liverpool Street - Stansted rail line. This would have reduced journey times to Stansted Airport by approx 5-10 minutes and added the capacity for more trains. However, the plan has been shelved for the next 5 years, due no doubt to the decline in Stansted Airport passengers.
There is also the possibility to add a second tunnel and track into the airport, which would again decrease travel times marginally and add capacity. This would need funding from the airport.
Beyond that, there are pie / sky 'thoughts' for a hispeed rail line to Stansted / Cambridge. Not before 2050, I would think.
Last edited by answer=42; 17th Oct 2012 at 07:47.