For big trips, I would only take medium format. I can't carry enough film holders for a day of good shooting, nor do I want to spend the time every evening loading and unloading holders. On my previous overseas trips, I found myself shooting about 30-50 frames/day (3-5 rolls of 6x7) which is just not feasible for me in LF but is trivial for medium format.
Can you get a 70mm back for the 'blad? That stuff is compact: you get about 70 frames of 6x6 (without reloading!) in a little metal can about 3x the volume of a 120 roll. Developing can be a chore though.
For shorter trips and especially where you don't expect to get many shots per day, sure, take the 4x5. I'm going to Perth for a week tomorrow, and I will be taking my Toyo 45A, 12 holders, 3 lenses and a couple boxes of TMY2 all in a little backpack.
Edit: while I like markbarendt's Option C, transport might be an issue. Your film and cameras should only be in the carry-on luggage when flying and I certainly can't fit both my LF and MF systems into one bag. They're each a whole bagful including film.