CX couldn't get the right regulatory approval to route through Moscow, so it looks like they've given up, because it's all gone quiet.
SQ apparently does very well from MAN. So much so, that there was talk of an additional 3 weekly frequencies, bringing the total to 10. I don't know why the MAN-ZRH-SIN flights have been pulled, other than it's reported that they're not as popular with passengers. Having intermediate stops is no longer really a profitable way to operate.
Nobody seems to know about SQ's plans to replace these two flights, but they are currently taking delivery of 777-300ERs (not sure how many). I think it's pretty safe to say that MAN will receive at least a daily direct 777 in future.