It would be nice to connect a lot of these density centers, I agree. But, I thought this was a list of likely projects in the next, say 25 years. Skyline is poorly designed but actually has quite a lot of office, residential and retail and the whole Baily's Crossroads area will redevelop as a dense node before Tyson's gets connected to this line (is my bet). Ridership will not be an issue on the Pike. The line would be replacing probably the most heavily used bus corridor in the system.

There is still unmet demand for public transport in many places. For example, the owners of much of Skyline (Vornado) runs private shuttles (although anyone can get on) on 20 minute headways from Ballston to Skyline all day due to the demand.

Also, I'll say Tysons has a long way to go before it can be a successful transit-served area. You could put the line in, but the design of the place does not support arriving by transit. You can't walk anywhere easily or comfortably. People say transit to Tyson's because the traffic is such a mess, they think that will help. But the traffic is a mess because of the

1)culture of driving,
2) large amounts of free parking
3) Everything is so spread out
4) roads have been widened making hostile walking enviro.
5) Uses are not integrated
6)... there are more variations on these themes

In short, good luck.