My hotwife has asked me to suck her lover

My wife has always been a hotwife. I have enjoyed sharing her in mfm, ffm and mfmf fun but in addition she has a couple of other lovers she meets alone. I have also got a FWB. We are happy with this situation and have been married over 10 years. Recently she has brought her two lovers to our home (not at same time), not when i have been here. She has now asked if i would join them, not to fuck but just to watch and to suck her lovers hard. This is a change and would be the first time i'd not be participating. If feels it is moving from a hotwife situation to a cuck situation. I am 100% straight ,never touched another guy's cock in my life.
I say jump on it while you can. I'd love to be in your position