I would ask your wife the question “Why?” If you haven’t asked, her answer will give you much more to go on in evaluating whether you want to head into expanding your relationship in this way. If you are conservative, a polyamorous or swinging lifestyle will be a significant reality shift. If you trust your wife and have a solid relationship then moving into additional sexual relationships can be fulfilling and powerful. If you have challenges in this realm, then you will surely meet them on the road.
Ultimately, what I believe you should do is have some serious heart to hearts with your wife. Understand her desires and intentions and ask the hard questions (and answer them too). If you decide to move forward, do so in constant communication and grow together.