I'm thinking it's Up Aerial, actually. Forward Aerial (at least in Robin's trailer) appears to end its swing at the angle where this move hits Mario. This move also clearly continues past that point doing an arch over Robin's body. I could be wrong here, after all the footage in Robin's trailer very well could be cutting off the end of the move it shows, but call it a hunch.
As for the landing lag, there was 2 frames, which is 4 frames in real time, as Youtube videos run at 30FPS. 4 frames is normal landing lag. I think the move just finished before Robin landed. Certainly looks like it IMO.
Now about Nosferatu. This has me scared. Legit scared. Let us all pray that grab-release shenanigans aren't as gamebreaking as they were in Brawl. Because if so, this could mean terrifying followups. The worst case scenario being that Sakurai gives certain characters inexplicably longer release animation frames than most characters like in Brawl *coughpoorNesscough* which could lead to more Nosferatu. If that were to happen... I could see Robin having some HIGHLY advantageous matchups. But if the followups off of grab release are kept sensible or just plain non-existent then it should all be good.