Yeah we have seen Zekrom twice(this one in flashback or story), so yes he definitely needs to get more love. Maybe Cedric will give mention to Reshiram as well. I definitely have thought of the scenario where Ash uses one of the two dragons. I don't know if it would be Zekrom(cause maybe N secretly ordered Zekrom to zap Pikachu) or maybe Zekrom was doing something of it's own will like maybe marking Pikachu some how to keep track of Ash progress.
If you notice it actually looks very similar to the costume Ash was wearing in BW040 - Movie Time! Zorua in "The Legend of the Pokemon Knight"! So I can't help but think that isn't coincidental.