Hi Morning Twilight
Polyamory can be a very scary thing and more so for someone who doesn't understand it. Before 'coming-out', which is a bit like laying all your cards on the table, why not introduce your wife to the subject from a distance? Has she even heard about it? Many people haven't and even if they have they often have very mixed up ideas of what it means and how it works.
I'm sure there are many ways you could start showing an interest in it without having to completely "come out". There is so much to learn and it's great that you have the opportunity to learn before you actually get involved with another person.
Many people think that if their partner is polyamorous they have to be also but this is definitely not true. I am one of many people who have remained monogamous and happy with a partner who is polyamorous.
Baby steps; just start the conversation and see where it leads, you may be surprised