Football is the most popular sport is the US for the past 30 years. It's popularity rises while baseball popularity decreases. The two aren't comparable.
Not only is football here to stay, it will continue to get more popular . . .
I disagree. I saw what Minstrel wrote, and I see that side of it. But it won't gain in popularity. It'll go one of two ways:
1) It'll over-saturate itself, like it's already becoming, and people will want to move on.
2) Eventually, the talent pool will dry up. You really can't make tackling anyone "safer". The parents will pull their kids out. And whether the bigwigs want it or not, the product will suffer and fans will simply go away and find something else.
Think of it like Facebook. It started out as this hip new, everyone has to have it... now it's so saturated, in your face, that people (And it's a growing amount) stray away from it to something else or nothing else. Granted, some of that is for the privacy aspect... but for others they said "That's just too much, It's too much." and left.
I see it happening, not because of my hate for the sport, but because we're a society that can only take so much before we need a reprieve. Baseball was HUGE, and it went away, when I'm sure most thought it never would. (And by away, I mean lessened in popularity). I really believe that will happen in football.