The double Syaoran actually reminds me of Chobits... Where Freya wants to take Chii with her and get both of them to be deleted permanently, while Chii wants to be with Hideki and decides to stay, even if it may be painful for both Hideki and Chii.
Maybe when both Syaorans are going to be eliminated or something (assuming the real Syaoran is actually just the other half), the real Syaoran will decide to live on even if Sakura will never remember him, and the other one will either vanish or become one with the real Syaoran (like Rayearth where Hikaru accepts her darker self).
I doubt Sakura will ever remember Syaoran, but I have a feeling that at the end of the story, she'll say something like this:
"I... even with all the memories gathered, still cannot remember you."
"I know..."
I don't know how things will be if I can remember, but I know I am happy with what matters to me, what is here with me now!!"
"!?"
"I want Syaoran to be with me! Even if I may never remember what happened between us before, I still want Syaoran to be with me!" Sakura buries her face into Syaoran's chest.
"Yeah... I want to be with Sakura, too..." Syaoran holds Sakura in his arms...
Um... Come to think of it, this is kinda like Chobits' ending...
Hopefully, Syaoran and Sakura will travel the dimensions together even after the feathers are all collected, doesn't feel right for these five characters to go on their separate ways afterwards... an occasional visit may be nice if Sakura retains her power and sending post cards or letters to Kuro and Fai through wormholes.