Don't know why a couple would get married on a DC Metro train, but, hey the tickets ares cheaper than paying for a church or building.
As for the Silver Line, Phase 1 should be operating by early 2014 (figuring the December 2013 date will slip a bit). If Loudoun County opts out of Phase 2, it is expected to cause a 1-2 year delay in putting the job out for bid as the agreements have to be redone. There would be some adjustments to the engineering and bid package, but it should be pretty straightforward to chop the line off pass the Dulles service yard and increase the parking capacity at Coppermine/Rt. 28. But there is too much support in Fairfax county, the MWAA, the developers, and in the overall momentum not to proceed with a truncated Phase 2 to the airport. With 2 fewer stations and several miles of less track to build, the construction time for Phase 2 could be shorter and make up a bit for the delay in starting construction.
The Silver Line to the airport is likely to be in revenue service before the East Side Access project in NYC is running LIRR trains to Grand Central. Other than the Second Ave subway, those 2 are the biggest transit megaprojects underway for the eastern cities that I can think of. So which one finishes first?