If your wife is unsure, then it means she hasn't said no so it's certainly worth broaching the subject again, particularly if you believe that she is interested in swinging for herself. If it's likely your wife will say yes only to please you (or get you off her back), then leave it alone. It will only cause problems if you end up wanting to include swinging regularly and she absolutely doesn't.
Try discussing swinging in a non-committal way. Find out what sort of things your wife is curious about. Would she enjoy watching another couple have sex? Does she want to try girl-on-girl? Are there things that she is sure she doesn't want to try like watching you with another woman? Initially, only focus on what your wife wants to try and be resigned to limiting your own wish list until you get the ball rolling.
If your wife seems genuinely interested in experimenting, you can then look at meeting another couple or a single male or female, depending on what your wife wants. Keep your first meeting purely social and reassure your wife that nothing she doesn't want is going to happen. If she is keen to play with your new friend/s right away, then that's fine of course. Just don't put any pressure on her whatsoever or impose any of your ideas or wants quite yet.
Once you've worked out that your wife is open to meeting more people and playing, you can start arranging more playdates and perhaps look at attending swingers events.
As long as you keep your lines of communication open, you should have few problems.