Is the Sunday backlog of cancelled flights into and out of LHR being resolved? We arrive on Tuesday morning, weather willing.
I'm sure the airlines and the airport are hard at work trying to clear the backlog. The biggest issue the coming days will likely be that many aircrafts and crews will be out of position. You should be able to tell already if your aircraft is enroute to the States. If it is, chances are that it will be going back to LHR on schedule.