The OP question was about whether the guys would suck each other (not whether the woman would suck a guy, which is already expected in MFMs). And my answer is Hell yes, given that I identify so solidly as a cock-loving bisexual that it might be hard for me to agree to mfm/mmf if the other guy isn’t into at least a bit of mutual contact. I certainly haven't written any two-male threesomes where it doesn't happen, or at least lead to something later.
From what I have gathered on the forums here over the years, Manda’s perspective is an extremely common one. Many (maybe most!) women feel threatened or insulted if the guys' activities with each other take the focus of attention off of her. So while MM contact can be part of the action, the woman needs to remain the center of the action, or disaster may result.
That means that any touching or sucking between me and the other guy would likely be fairly brief and not go all the way to orgasm. Also, many women seem to get a special hot thrill in coaxing guys into kissing each other (see: Challengers for just one example), and I'm totally into that if the other guy is. The only anus likely to be penetrated would be hers, though, except for the rare situation where she insists on watching us men fuck. Which I would still totally do if asked.
If the guy and I want more from each other than makes sense in the presence of a lady, the solution is not to embarrass her by leaving her out of anything. It’s to meet up one-on-one later without her! I have no problem with that.