币
A couple other thoughts on this. First of all, I forgot to mention this character is pronounced "bi" (almost identical to the letter B); it seems natural that "B" could become a spoken shorthand for "Bitcoin" the same way "buck" is short for "dollar". ("A small coffee, two packs of cigarettes, and a cruise missile. That'll be 37 B.")
If I know anything about the Chinese blogosphere, if Bitcoin weren't to push an official Chinese version of their name, a fairly likely Chinese name to spring up spontaneously would be 网民币 -
Wangminbi, "The Netizen's Currency", a pun on
Renminbi, "The People's Currency".
Previously discussed formats for comparison:
币2
币1200
币37.50
2币
1200币
37.50币
37币50