A 20th anniversary ad would be interesting to rekindle the Poke-flame inside of 110+ million people (that's kind of insane... that's ~1/3 of the population of the United States). As a fan, I would probably cry.
I would especially cry if they revealed "Pokemon Z," Gen 7, or more details on Pokemon GO.
Anyone buying ad time on the Superbowl knows that it's not enough just to air your ad for those 30 seconds. You want your ad to be news for as long as possible.
Pokemon is a marketing machine, they must know this. A simple ad for the 20th anniversary, no matter how tear-jerking it is, is not going to make news on it's own. Reveals of "Z" or Gen 7 would cause huge ripples in the fanbase for a while.
A flashy Pokemon GO insert coupled with new information, on the other hand, would appeal to everyone who has been with Pokemon since 1996; whether they are currently 4 or 40 years old. It would be especially favourable for them to release the ad then a press release a few days later to keep them in the news as much as possible.
That being said, Pokemon does do weird things sometimes. If they manage to simultaneously evoke nostalgia in former fans and excitement in newer ones; even if they don't stay in the news they may have a shot at finding a place in the American consumer consciousness... at least until the next ad plays.
If it helps widen the fanbase, though, I'm all for it.
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Edit: I also just want to say that the slogan "Train on" is kinda weird to me and doesn't really roll off the tongue. I don't really like it tbh