Most likely "LM/CZ-10". It is not a size competition with anybody in that "I beat you with bigger numbers". Example is that China still call J-20 a fourth generation fighter although US and Russia call their counter parts fifth generation. Not bothering fancy and trendy name is a clear demonstration of self confidence.As an aside, I hope this 921 rocket would have a more creative name than just "Long March Heavy". We already have the triple-core Delta IV Heavy and Falcon Heavy. Maybe "Long March 555"?