If Metro Vancouver had opted for a modern big city train, IE something like the elevated Metrorail_in_Miami-Dade_County, better future capacity would have already been built in.
http://miami.curbed.com/archives/2014/01/28/miami-getting-shafted-on-money-for-trains.php
Just because SkyTrain is considered LRT, the stations could have & should have been designed to eventually be 153m or just over 500 feet in length. Thus, the original little SkyTrain cars should have been able to form an 8 car train, with a provision for 10 & 12 car trains. Not just 2, 4 or 6 little car trains. That would have been slightly longer than a 4 car Miami_Metrorail_train, which is 300 feet.
http://miami.curbed.com/archives/2013/09/17/-all-aboard-florida-wants.php
http://miami.curbed.com/archives/2013/05/08/miamis-downtown-train-station-breaking-ground-this-year.php
http://miami.curbed.com/archives/2013/09/17/-all-aboard-florida-wants.php
http://miami.curbed.com/archives/2013/05/08/miamis-downtown-train-station-breaking-ground-this-year.php
"The cars are semi-permanently attached in married pairs, and joined up to form 4-car trains, which is the normal train length, although 6-car trains are also possible." https://en.wikipedia.org/wiki/Metrorail_(Miami-Dade_County)#Rolling_stock
"The cars are 75 feet (23 m) long, 10 feet (3.0 m) wide and have a top design speed of over 70 mph (110 km/h)." https://en.wikipedia.org/wiki/Metrorail_(Miami-Dade_County)#Former_fleet
A 6 car train would be 450 feet, the same length as a TTC subway train. A 9 car Montreal Metro train is 500 feet long.
trains
