Plots, theories... heck, I'll clear them all up.
Alright, I've decided to do my best to clear some things up. The bulk of this article concerns Yuko, Clow, Eriol and anyone else who knew what would be happening.
What gets me is that Yuko has said so much and then gone back on herself so we don't know if much of what she says about Clow or his descendants (save for Fei Wong Reed and the creation of the Mokonas with Clow) is true.
For example, Yuko's lied before, about knowing Clow Reed. In chapter 3 of xxxholic she said she's not met Clow Reed, Sakura or Syaoran. Then in volume 2 she goes back on this, saying she had met him and that she and he had created the Mokona Modokis (although she's still insistent she hasn't met Sakura or Syaoran). A special furthers this by saying Clow and Yuko went to meet the Mokona of Cephiro (from Magic Knight Rayearth). She's fed quite a few lies about the place, why give up the habit of a lifetime (Yuko can give correct info out, sometimes without a price, but I guess lying doesn't have any price attached to it, unless you count how much the listener believes her). I think she lied knowing that Syaoran and Sakura were old enough to have a son, but she also knew time-space was beginning to collapse somehow. This doesn't carry over into Tsubasa yet, I think, because the group had travelled into the past and future worlds to get feathers (although Mokona has time travel). It could also be that 'Syaoran' is from the future and was sent back through time to find Yuko before any of the events happened, so as to prevent them from happening at all, although that's unlikely. The only thing Yuko seems to have told the truth about in that respect is having not met Sakura and Syaoran.
But then if you think about it, Clow's lied too. He claimed he saw Yukito and Sakura getting together, but if he was preparing for Syaoran and Sakura from Clow Country, then he already knew Syaoran and Sakura from his world would end up together. Perhaps he didn't see their kid getting embroiled in TRC's events (perhaps Clow saw Syaoran himself getting tangled up instead), but until Clamp finish TRC we won't know. In addition we should be given further explanation on just what Syaoran and Sakura were doing between the years of Syaoran's return to Tomoeda (end of CCS Volume 12) and now, and just why the heck they'd let their own son get embroiled in this (and get involved with Sakura in the first place).
Also I wish to point another thing out. I'm surprised many people either stuck to 'Syaoran is Syaoran Li' or 'Syaoran and Watanuki are the same guy' theories. Consider all the evidence of 'Syaoran' being Sakura and Syaoran Li's son. This is IN ORDER OF RELEASE
xxxHolic ch 3 - Watanuki finds the Sealing Wand replica (but for some reason not the real one) and Yuko comments on how she 'wanted' it. Past tense use. Tiny bit, but that past tense implies (albeit vaguely) that she already has the original in her possession.
TRC ch 121 - The first appearance of Syaoran Li's rashinban glyph, as the seal on the right eye of the Clone Syaoran. However, considering Clow Reed's glyph has appeared, people may have dismissed it.
TRC ch 123 - The first sight of 'Syaoran' using his father's glyph, sword, and 'Raitei Shourai'. Some fans mistake his appearance as Syaoran Li himself (quite rightly so).
TRC ch 144 - Sakura calls him 'Syaoran-kun', and states that "Moko-chan told me you too are called Syaoran-kun". To which 'Syaoran' replies "No, that's... well, right..." (NOTE: Why would Syaoran Li deny his own name??)
TRC 170 - Seishirou states 'Syaoran' is just like his father. In the anime, Syaoran Li said his father was already dead, and that is implied in the manga as well. (At this point I started to cotton on to the fact he may not be Syaoran Li after all, and there was certain significane in his remark - and then Syaoran Li's name started tugging at my mind)
TRC Tokyo Revelations 2 - Sakura Kinomoto makes an actual appearance. Some fans take this to mean she is dead (but forget Yuko herself stated that Sakura and Syaoran live in HER WORLD, and also forget Sakura was not in the manga, instead it was countless spirits who lead Sakura back to the group)
TRC 188 - 'Syaoran' states he knew Sakura from 'seven days before her seventh birthday', and that eliminates any chance of his being Syaoran Li (he is 14, and knew Sakura for 7 years each continuity (totalling 14 years), so he was 7 when he met her)
TRC 189 - The big break. 'Syaoran' recalls being sent to Yuko as a seven-year-old kid, giving his name as his father's (Li Syaoran) and learning his mother (Sakura Kinomoto) already paid the price to allow him to travel dimensions with the Star Wand.
Wow, I'm surprised it took 189 chapters to make some people realise this. I came up with that theory well before 188 came out (not 189).
I've also got another thing to add. Everyone is saying that 'Syaoran' can't love Sakura in 'that' way. They forget a few things. 1 - the feelings the clone had towards Sakura belonged to the original (because it was the original's heart which resided in the Clone). 2 - 'Syaoran' can't have true romatic feelings for someone who is his mother in his world. I think I should draw your attention to something made clear a lot earlier. Fai pointed something out in Piffle World when he was talking to Kurogane about Princess Tomoyo.
"Except... that's not the real her, is it? She may look like her, but she's a different person."
Kurogane responded by saying:
"It's the same face, however, it's not necessarily the same person."
And also people were saying that since 'Syaoran' isn't Syaoran, that relationship can't happen. I think Clamp are trying to deliberately break the 'soulmates' stereotype that they themselves have used in their works.
I hoped TRC 190 would give us his real name but apparently not. It's more flashback, according to the spoilers.