shine,
As far as I know, USCIS will not cancel B1 VISA as its a non-petition based VISA which was not approved by USCIS but your home country consulate.
When you go for H1B VISA stamping at the consulate, the VO might cancel your B1 without prejudice.
As suggested by your employer, its safer to be back home so that USCIS won't question your intention of extended stay in the US on B1 VISA.
Thanks,
Sujith