First, I wish to thank each of your thought provoking responses. I now see that I've made assumptions about poly generally from reading active posters on the forum that are NOT reflective of poly overall and will try to keep this in mind, going forward. My assumption was that my wife was very unusual, even among poly people for feeling drawn to poly without being actually having a actual potential new lover in view.
It also helped to learn that the concept of poly occurred with some from even early age or from reading fiction which depicts a workable model. I may have to read some Heinlein, but wonder which would best express his concept?
We went out for our second very small poly meet (a total of five people) last night in a quite coffee shop. The other M+F couple attending also offered a helpful perspective in coming out of a broken FMF triad, that broke up badly, but so valued the triad dynamic that they are actively looking to restore that model with another. As someone considering this on a trial run basis, it was revealing that even with the pain of the breakup of the triad, being a solid couple, still left both yearning for a return to a working triad. My concern being that once my wife should have really happy times in a V, that should we go back to being just a couple, she'll be yearning not for an idea of what it would be like, but recalling what it was like, and that this may be less bearable.
The facilitator was very encouraging for my wife having her first date scheduled for tomorrow (Sunday) night in a coffee shop and helped me some with my concerns. I confessed that for her sake I won't have a rooting interest, but was feeling a little guilty for at times thinking if she discovered that first date guy wasn't a good match, it wouldn't be so bad from my pov, but don't want her to be unhappy either.
One aspect in all of this that I am very thankful for is that she did tell about what she wants and why, and has been willing to take things slowly and educate us. Had she acted deceptively to explore her yearning and shattered our trust, or made her intentions an ultimatum, than this would be either very much more difficult or unacceptable. Her actions show me the sincerity of her love for me and assures me of the importance of our relationship. I'll keep this in mind while she's out on her date and will anxiously await her return.