N is definitely Wally, 10 years later.
honestly, I don't see where this came from. frankly, the only similarities between them are the hair and eye colour, which is a huge stretch when assuming it to be the same character. first off, why would Wally start doing what N is doing 10 or whatever years later in a completely new region? why does he have none of his Pokemon from RSE? if Pokemon are supposed to be friends like he said, you would assume he would at
least keep his first Pokemon (Gardevoir) with him, as they would be best friends at that point.
basically, in order for it to be Wally, he would have to: abandon his friends (which included his Pokemon) and family in Hoenn, change his name, go to another country and start building a team of new Pokemon despite already having Pokemon in Hoenn to being with (which would have been Powerful enough already to help with his plan). none of this seems like anything Wally would do. he seemed pretty adamant on being a trainer in RSE, so you would assume this ambition would continue, not reverse to wanting battling to end in general (which is what I gather N wants).
from what we know about N, his personality is much too different from Wally for them to be the same person. if N is Wally, then that's just a bullshit twist that has no reason to be there.
that being said, I could see him being Wally's son or something...