I am a U.S. citizen and my wife is a Kenyan citizen. How long should we expect to wait for Visa.

You should work with an Immigration attorney who can enter an appearance on behalf of you and your spouse in order to process the case from start to finish so that no delays or no snags occur. If you are a US citizen sponsoring your foreign born spouse through consular processing, it takes about a year or a little less. Counsel anywhere in the USA can help you.