Yeah, it's Syaoran and Sakura...
Plus CLAMP says they are gonna put in characters from many of their other works- in different form.
From what I remembered, CLAMP REALLY, REALLY enjoyed writing short comedies of what the characters would have been through should they be in a parallel setting. RG-Veda: Soap Opera Ver. was funny... Yasha was a cop, and Ashura was a genie in a tree trunk, and Kochaku is Yasha's mother-in-law
Almost forgot, I remember that recently, CLAMP drew another short comedy where Hideki and Chii accidentally entered Cephiro...
So there you have it, CLAMP's joy in mixing up their characters in various settings, which is something I'd think about, too, for many other fictional characters.
I remember them saying something about making an anthology of their past works, and then came up with the idea of making another manga where they can freely put in old stuff anywhere they want (explicitly or subtly)
I was very interested in Tsubasa when I see Syaoran&Sakura would have been the fact that I am finally able to see some of my favorite characters here, NOT DEAD-- A.K.A. : Sei-chan, Oruha, Sorata, Souma, Kendappa, Ryu-chan <-YES! Ryu and Sora-chan are my favorite, and I'd like them alive and well, and it's good to see Ken-neechan no longer a murderous psycho