So there are a number of factors here:
1) Do the liberals really "need" to keep that particular campaign promise?
No party actually "needs" to keep any promises - witness Jean Chrétien in the 1990s: we still have the HST/GST and we're still in NAFTA. But this is a fairly easy promise to keep - witness Prime Minister Chrétien, again, and the EH-101.
2) What happens when the aerospace lobbyists get their claws into the new government (mainly based out of Montreal, Winnipeg and Toronto....Liberal seats in the last election)?
There are always ways to buy off special interests
3) Does the government want to limit expeditionary capability for future governments, like the conservatives tried to limit taxing and spending by future governments?
That is, probably, the farthest thing from the politicians' minds, right now. I expect the PCO national Security Advisor to raise that point, but it will be just one of many
4) What happens when the NATO allies get their input in?
That can matter: witness Prime Minister Pierre Trudeau's "walk in the garden" with Chancellor Helmut Schmidt which kept us, in a very limited (essentially useless) way in NATO's European Command and got us new, German, tanks
5) Does the government need to have a minimum contribution into NORAD, what is it and what are the requirements?
I don't think it is detailed down to that level
6) What is the required role for the new fighters, just NORAD contribution, expeditionary, other??
That's the government's decision
That has a huge impact on the type and number of aircraft for the replacement. I think the RCAF has boxed themselves into a corner. I wouldn't be surprised if they came out and said we need more aircraft if the F-35 isn't an option.
This is a golden opportunity for the DM and CDS to craft and present a CF wide vision to a new government, free of the "I'm more special than he is" stovepipes that characterize high level policy making in DND today. What [size=13pt]is the world situation, today? What do we really need? For what roles/missions? How jointly shall we fight and, therefeore, how jointly should we be organized? But, I expect we'll let newly elected politicians have the final only word.[/size]