Having recently ridden on Network Rail here in the UK between Portsmouth and London, I'd would definitely say that it's worth it to it get the Windsor-Quebec Corridor High-speed link going, starting with Toronto-Montreal section (one may want to consider another high-speed line between Ottawa and Montreal).
Express Trains
For now, regardless of how long from now the high-speed rail link will come, Via Rail really should get some express trains going (dedicate some of the
existing trains for direct, non-stop service between the major cities), which may make it more attractive (I know that in some cities where express buses were recently laid on, ridership volumes shot through the roof, even in THUNDER BAY, so a similar effect may happen with the trains - on a larger geographic scale though).
Oddly enough, there is still no express trains between Portsmouth and London, even though the line is quite popular in terms of use - in that instance, I'd have it stop Portsmouth Harbour, Portsmouth and South Sea, and Fratton stations to fill up the train on the Portsmouth end to pick up Portsmouth passengers, and then go straight to Vauxhall Station (near MI6 HQ) and Waterloo Station (across the river from Westminster) in London, where most of the passengers would likely get off. A similar scheme could be used for Toronto-Montreal and Ottawa-Montreal, and if possible, Toronto-Ottawa later on. An effort should be made to have direct shuttle service to/from major airports and other transport hubs in those centres, if they can't be served directly by the trains. However, in the case of Network rail in the UK, some stations need to have bypass tracks built around them to allow express trains to pass by them without getting held up behind local "collector" trains, which will be difficult due to the narrow rights-of-way. CN's rights-of-way are usually wider, so implementing express trains might actually be easier (ironically) for Via Rail than it would be for UK's Network Rail, where Via would start to have an "express-collector" train system.
Channel Tunnel Style Vehicle Haulage Service
Via should also look at the possibility of providing vehicle haulage service (number of vehicle cars would be determined by expected demand), similar to the Channel Tunnel Train between Dover, UK and Calais, FR, for those who are making a long trip and plan on staying at the other end for more than a couple of days (renting a car starts getting very expensive when it's more than a few days). Such a move may help attract passengers to Via, who's destination is a good distance from the nearest station (i.e. Thunder Bay-250km from Armstrong Station), or those who are making a
long-distance trip , like me, and plan on staying at the other end for a little while.
Real-World Trip Scenario That Many May Encounter
For instance, after I fly into Halifax from Heathrow on Saturday, then I'll be driving (my car) between from Halifax to Cornwall, ON, (in one go) to pickup my friend upon doing an overnight rest stop there, then drive on to Thunder Bay, where I'll stay for 2.5 weeks, except for a trip further on to Brandon, MB (for a few days) in the middle, and then near then end of the month, drive back to Cornwall to drop off my friend, and boot it back to Halifax to catch my return flight back to Heathrow (I have to do a few more weeks of work in the UK before returning back home to Halifax for good). On top of that, Heathrow is two hours away from Portsmouth (be it by train - which has no express service, or by bus - unfortunately, the Hindhead Tunnel on the A3 won't be finished until summer - it's a 1.83km long tunnel under the Town of Hindhead, which will be the longest non-estuarial road tunnel in the UK).
How An Improved Via Service May Play Into This Scenerio
As much as you guys may rightfully laugh about my transport situation (honestly, it has me laughing

), if it was possible fore me to pay an extra few hundred dollars to be able to park my car on a vehicle car on the train (Chunnel-style) in Halifax, I'd probably probably go on the train from Halifax to Armstrong Station and have my friend catch a Cornwall-Montreal bus or train and join my train in Montreal (unless I decide to overnight it in Cornwall, where I would de-board in Montreal and re-board in Ottawa). If car-loading service were to ever be provided (in a feasible manner), I would only expect car loading service to be provided at major cities (or nearest station to a major city), i.e. Toronto, Ottawa, Montreal, Sudbury, North Bay, Sault-ste-Marie, Thunder Bay (at Armstrong Station), Dryden or Kenora (maybe), Winnipeg). Such a service would really cut down on the driving people would have to do, and it may attract more passengers to the trains, whilst allowing them to drive around freely at their destination without having to rent a vehicle (and also bypass sections of highway the are often congested or that would otherwise be in need of a major upgrade for safety and efficiency reasons).
Closing Caveats
Such a system would still require a significant amount of public consultation and feasibility studies, on top of convincing politicians to support such a system based on real-world priorities (and no just for the sake of getting votes). However, it's still worth it to discuss this.
Regardless, if Via wants to remain viable, they need to completely overhaul their service now.