What will happen if the court date appears after the Expiry of a B1/B2 for a misdemeanour charge

Probably nothing as far as immigration law is concerned except you will be out of status and if long enough so, barred reentry. What could and should have happened had the immigration laws where properly enforced? You could have ended up being detained by ICE because you overstayed your status.

Do you really mean expiration of visa, or expiration of stay?

You should first talk to your criminal attorney, who is representing you, and decide whether the handling of the case requires your presence.