I have to agree with the above poster. Prior to learning that your wife was bisexual did you have a desire to have an outside relationship? I am close friends with a couple (they are admittedly swingers) where this situation occurred. She wanted to open things up (with men and women), but he was content to be mono. They did the whole swingers scene for a couple years and when we saw them a couple if months ago she told me they were getting out of it because he had trouble meeting women. All I could think was how that was the result of him not actively desiring that life style. He went along with it, but more to please her.
Would you be comfortable letting her experiment with these feelings without you getting an outside lover? Are you interested in a possible triad with a woman that connects well with both of you? I think those are things to consider first rather than feeling that because she is doing it then you must also find someone.