I have not been on that new train, so I do not know how full/empty it is. I am not disputing your claim that it is full even though at 100 people per car the capacity of that train is 300 people or more. My assertion was that in the pm peak the Harriman express(there is only one that skips all stops to Harriman) recently was only 3 cars and there were not many standees.
East of Waldwick is 3 tracks, but in my opinion given the way our current politicians behave and extrapolating into the future you will not get a third track west of Waldwick in your or my lifetime. Even though the right of way is there as are all bridges, the incentives for the politicos are not there. Why would a NJ politician throw support behind a third track when it will be used by NY trains to speed by his NJ constituents? Why would a NY politician agree to spend what would be on the order of $100MM for track work outside of NY state? Even then, good luck with the 5+ years of litigation by NJ residents trying to delay and cancel the project given that there is no benefit for them. Yes, they left all that space in the middle of Route 17 station for a third track, but that was because the transportation planners/engineers knew what they were doing so as not to preclude future expansion, not because they were certain that third track would be funded by the politicos.
As for double tracking in NY. Yes it can be done. Yes, politically it is much easier. Yes, they allowed for it during the recent upgrades to PTC. What does it buy you? There are very few meets north of Suffern. Nothing that is a problem now or cannot be solved with another 2-3 mile siding. There is no need for trains passing each other either (other than the case of a train breaking down). If you double track through a station you need to build a second platform which will trigger ADA compliance, so elevators will be in order. That makes the double tracking a very expensive proposition in terms of cost-benefit right now. If ridership doubled from current (or better from 2008) levels, then it becomes much more defensible. I will give you this much: if it was double tracked, then that new train which gets to Middletown by 4:20 would actually be able to make a revenue run back to Hoboken. Right now it deadheads back to Hoboken because otherwise it will get in the way of the pm peak hour expresses north of Suffern.
And as a side note, it is my understanding that the ridership still has not recovered to its 2008 peak.
And again do not take me the wrong way. I would love to see improvements on the line in both NY or NJ. I just do not see them as realistically happening any time soon.