It has happened for us .. and became a regular feature with my wife's last lover.
She was kneeling and had the head of his cock in her mouth, and expertly sucking him.
He told me to come over and kneel beside her. My face was just inches from my wifes face and his cock.
He then pulled his cock out from her mouth and holding it at the right height turned slightly and brushed it across my lips.
I opened my mouth and he pushed it in and I sucked it for about a minute or so.
I remember my wifes little gasp, and later said how how it was. After a minute he pulled it out, and my wife closed her mouth round it.
After tha, it became regular.. he would have my wife on all fours, totlaly bent over,
and then postion me with mt head close to her arse.. and pull out and have me suck him for a while..My wife would then be waiting, hot, and trmebling for him to finish with my mouth
before thrusting back into her pussy.