Based on the production timelines of films, television would have seen a larger impact first, but considering how far in advance studios are now planning films, a writers strike would have essentially destroyed the release calendar as we currently see it.
If no deal had been made a strike from the Writers Guild would have sent a shockwave through Hollywood.
Writers on everything from late night talk shows to major motion pictures would have ceased working almost entirely.
While this would only have had a minor impact on films that already had completed scripts, anything that was currently in the writing phase would immediately cease moving forward.