It is alarming that the other guy is saying something so serious so soon.
I get you’re trying to be supportive, but do you get what you’re saying here?
It's probably NRE talking. NRE makes us say crazy things. Either way, it's crossing a boundary. He should not be saying things like that until he has been in her life for at least a few years.
Yes, it could be NRE, but at the same time, people saying whatever they’re saying are dead serious, and don’t think they’re saying anything crazy. The whole idea behind polyamory is being autonomous and free with intimate relationships, and you are suggesting policing one’s thoughts and speech? Dictating what type of things can be expressed or within "your" time frame (of a year). Seriously?
Tell your wife you need her to slow down.
Because of what he said? She needs to slow down because lover guy enjoys/loves too much/never wants it to end? And how do you think that’s going to go over??
Isn't this the guy that, when you met him, he was just nice, but otherwise a loser? Is this the same guy you caught with your wife in your office space, with him doing up his pants?
It seems to reason it is the same guy, but is that relevant?
It seems that your wife has used poor judgment in who she picked out, and how she has conducted her relationship with him.
First of all, that’s super subjective. Secondly, who holds the rule book on picking partners and perfect relationship conduct?
If she was posting a thread here saying my husband dislikes or disapproves of my lover, you’d be saying, "Fuck him, it’s none of his business who I date or what we say or how we fuck." PLUS maybe she sees herself as some sort of love angel, providing love and sex to those forgotten by society… To each her own, right?

AND she might be doing society a big service, if you think about it.
I don’t remember how or why these people opened their marriage, but unfortunately, you don’t get to micromanage from the back seat of another person's relationship.