[Tony manages not to look at Bruce for as long as possible, but finally he sighs and puts down his sandwich again.] I'm no time travel expert, but...just because someone says something is going to happen doesn't mean it's set it stone.
[Just look at what Bruce and the others from the future did, coming back and rewriting the timeline. If Bruce is worried about his future self's feelings for Pepper, there's really no point. There's no guarantee the same things will happen now that the past has been changed.]