Chinese Yuan to start trading at the Merc.

Not sure if this has made a great deal of news yet, but it was announced today that the Chicago Merc will be beginning to trade the Chinese yuan starting August 27th of this year.

Who in the world would take the other side of the sell?

You assume that:

A) the exchange rate will not have changed prior to the CME contract launch.
B) the yuan interest rate will not be punative
c) there is a legitimate exchange rate discrepency
d) that the contract will operate in an unrestricted manner
e) that non-chinese banks will be permitted to trade the product
f) that a sufficient arbitrage machanism exists to maintain spot/futures contract price parity
g) that the product will make it to market on the specified date
h) that the market will be liquid enough to allow for speculative activities

In short, until the contract is open for trading, you shouldn't assume anything.

Do you even follow the currency market?

a. the exchange rate will not have changed prior to the CME contract launch.
You've missed something pretty big in the currency world the past few months. Here's the latest three changes in the USD/CNY from the past three days.

China yuan ends at 7.9987 to US dollar vs 7.9962 in exchange-traded market

China yuan central parity rate set at 8.0026 to dollar vs 7.9975

China yuan ends at 7.9964 to US dollar vs 7.9970 in OTC trade

Ulitimately, the BoC is pushing their currency higher vs. the dollar. You did know that, right?

b. the yuan interest rate will not be punative
I'm more focused on the flow of funds out of the U.S. and into China, not interest rates. Besides, interest rates in China are not the latest focus for the BoC. Instead, they have been moving reserve requirements. Perhaps you missed that as well:
China hikes banks´ reserve ratio in latest move in liquidity battle

c. there is a legitimate exchange rate discrepency:
I never mentioned an exchange rate discrepancy (you're the one assuming something). Instead I focus on the fundamentals of currency trading and the flow of funds. Perhaps you shouldn't assume anything with how I trade.

d) that the contract will operate in an unrestricted manner
The theme of your reply is: Lack of research.
Try doing some here:
Chicago Mercentile Exchange News

e) that non-chinese banks will be permitted to trade the product
You're kidding, right? Did you put any thought into this at all?
Why would there be a U.S. contract open to anyone with an account if you can't trade it? For the record, as a hedge fund manager, I have a prime broker and deal with 6 other brokerages daily (options only). Several of these brokerages are already involved in dealing with the USD/CNY.

f) that a sufficient arbitrage machanism exists to maintain spot/futures contract price parity
See above.

g) that the product will make it to market on the specified date
The CME wouldn't have announced something is trading in two months unless otherwise. A quick call to some friends on the floor confirms that they are ready to go.

h) that the market will be liquid enough to allow for speculative activities
This all stems from your point of view. Regarldess, trades can be made on the currency. Spreads aren't likely to be too wide.