For trade reasons alone, I can't see this happening. If it does it is shooting themselves in the foot.

I never liked to use the chinese TOM version of skype, so I always ended up using a online encrypted web messenger, or skype portable which runs from a usb stick and doesn't need to download anything extra.

If skype is blocked, I'm not sure Trillian will work in China, I used to use it and couldn't access facebook chat, but everything else worked fine.

I suspect the reasons for this are more commercial than anything else, let the money go to their own telco companies, and not let the foreigners make the cash...