But once again, the problem with Superman is that the world he comes from is basically THE SAME he is in right now. Most of the big events happened here, too - for example, there was the Blackest Night, alien invasions and so on. What secret knowledge could he come up with which people of this world haven't lived yet, or couldn't understand on their own? President Luthor? Does ANYONE could seriously think that is a good idea, in New52 or E-1 or E-whatever?
The situation is particularly messy because - and that's the writers' fault - they never provided New52 with a streamlined history. It's been FIVE years, and up to Superman Rebirth we NEVER knew if Death of Superman occurred on this universe, too. Quite frankly, that's inexcusable - and that's the reason this "comparison between continuities" can't really work: new52 history is simply too frail.
Wally West is in a slightly different position because, in fact, he DID miss something from the previous continuity - Linda, his family, and so on. Don't get me wrong, I don't think that giving him a deeper knowledge of events which haven't occurred yet is a good idea (well, if he hasn't lost such memories yet): in fact, I think that this is confusing as hell and all the possible stories which come to my mind have extremely creepy consequences (like, Wally meeting Linda Park and slowly making her fall in love with him because his knowledge of her tastes and their unborn children gives him an advantage upon her). But at least there is a possibilitiy for stories.
Superman is in a different position, though, because - once again - there aren't huge differences between his world and THIS world to give him an advantage about it. I think that they will simply put him as a New52 Superman stand-in - that's the reason I am pretty sure that Bryan Hitch didn't radically change the plot for his JLA stories in order to accommodate the presence of SuperDad.
Your second option is the answer to the first one. Nuperman has enough fans that he can't be swept under the rug, and he will always cast a shadow on SuperDad, at least for the foreseeable future and as long as NuLois is around. But SuperDad has some fans too, and he will have even more now that Jon's getting such a great push. And they can't sweep him under the rug, either.
At this point, all which comes to my mind (aside from one question, that is: WHY THE HELL did they have to create such horrible mess? I mean, think about it, there's literally zero reason) is what I have already said, that is: they need to find a way to create a unified continuity where the characters' memories are real memories of real facts. That is, something which they should have done in the first place.
The funny fact is that, if they had created this whole Superman doppelganger mess with a STORY in mind, instead of a simple gimmick, they could have made something interesting - this old Superman story comes to my mind, and it is an excellent example of what you can do with multiple Supermen
http://comicvine.gamespot.com/action...s/4000-121272/
But, as I said, this is not a story, but just a gimmick which they implemented for... Well, for some reason I really can't understand yet.