How do you feel about sleeping with someone other than your wife? How do you feel about your wife for putting the idea out there on the table?
I feel there are two types of poly - polyamory, where you believe you can love more than one, and polysexuality, where you believe you can enjoy sex with more than one.
Where things get tricky is that many people, myself included, start out under the umbrella of polyamory. Then boundaries get slapped all over the place. "It's ok to have sex, but it's not ok to fall in love." Unless your heart is literally wired to only love one person, you cannot stop love. Even if your heart is monogamous, nothing can prevent you from falling out of love with one person and in love with another.
In my relationship, we go for a middle ground. We do not feel we have the desire or time to actively seek love outside of our current relationships. We are polysexual, with the acceptance that love can happen and if it does, we'll deal with it when it comes.
I was with my ex boyfriend for five years and he initially suggested that we become mono/poly (where one is monogamous and one has other partners) so that I could explore my attraction to a girl I'd met. He (and I) had the belief that "as long as I come home to him, it's all good". Of course, 6 months later, I fell in love / lust / insanity and things got very messy.
So... if you can both acknowledge that love for someone else *might* happen... where can you go from here?
There are some resources on this forum; I think they are on a sticky thread on the main page. They have suggestions on books and websites to read.
If you believe that you cannot get everything you need from one person, then you might have one of the components to be happy in a poly situation.
For me, the main components of being poly are:
Honesty - no lies
Communication - get my needs and feelings out there
Empathy - understand and nurture my partner(s)
Dealing with insecurity - not letting jealousy take over
How do those things sound to you? Do you think that you are your wife take this approach to your marriage already?
I'll come back tomorrow and check for more details then!