Eriol I agree with above that he could be an author, or maybe amusician, something aristocratic and refine. Then again, he already is an adult in a way, so he must be prepared. Same with Kaho. I can see her being a priestess, or she could go back to teaching.
The rest is unoriginal.
Tomoyo I always thought would start her own company like her rmother, but with clothes, and be a world-class famous fashion designer. It's just fitting, you know?
Sakura can either be a housewife (If she has Syaoran for a husband, I think she's set for life), or take her place of her mother, being a beautiful model, of course, and mostly to distribute Tomoyo's fashion line. I can already see Tomoyo spazzing KAWAII!
As for Syaoran, I always thought of him taking over the Li Clan, be the leader, I mean wasn't he trained to be? The kid has a mansion and is loaded obviously. And he could also be a business tycoon XP. Something of high standards or politics at least, me thinks.
For Touya I'm not sure, but he's capable of becoming very successful, though the embassador one is a very good idea.
And for Yukito...um...wow, I don't know.