Marth:
http://youtu.be/e0ej06eP_uY?t=1m17s
Lucina:
http://youtu.be/MW6TpZPYd58?t=1m59s
It looks like Marth and Lucina both appear to have very little landing lag on Nair, this makes sense because Sakurai did state that their attributes were identical. He did say she was a little faster, but that could be referring to movement speed. I'm pretty sure what's happening here is that they are both entering landing lag and completing the full landing lag animation, since it's possible for landing lag to be different for each move hence how Bowser generally might have more lag when landing during an aerial than a character like Luigi or Yoshi. In Brawl, for example, there were even some moves with landing lag so short that you'd probably miss it if you weren't looking for it, such as Wolf's back-air. There may not be any aerials like that in this build but there are indeed some aerials with very little lag where you're able to follow up after a hit.
www.youtube.com/watch?v=wjbNBMOuNvE#t=50 Here's one good example.
www.youtube.com/watch?v=bryoKOZuyrU Here's another.
Even Bowser's Nair, despite not having the quickest ending when landing, still appears to have at least some potental for jump-ins and set-up
http://youtu.be/OD_ZnB8yJuA?t=16s I realize that Samus did manage to start-up her Fair here but it started up about the same time as he started jabbing, which means that if he was negative in this situation that it was very negligible, or his advantage was actually 0 meaning they both can act at the same time. He may not get any true combos but at least now he might have the potential for some good strings.
It may just be because I wasn't there myself, but it seems less like landing lag went up for everyone and more like the landing lag was just increased for certain moves with certain characters. It seems like a fair change to me, since it balances out the level of commitment players are making when using aerials as opposed to just being able to create a wall because of there being little or no lag and very small punishment windows overall. Some characters may still commit less than others but it'd probably be more balanced in general and even then, they would likely make up for it in other areas.
Hope this helped in some way!