Just looking at the dates for internationals, it appears we'll have four friendly slots before the World Cup: two in March; two in June before the competition starts.
Certainly the March matches could give an opportunity for a couple of the fringe players to get an opportunity, whereas the June slot will be similar to the friendlies we've had before the recent Euros.
The sides we play in these friendly matches will come down to who we get in the draw (most likely).