Hi,
Many applicants face the interview process. In a spousal sponsorship it is almost always because CIC doubts the relationship is genuine.
Your wife will receive a package containing the evidences provided.
It won't take 24 months. Last year when my wife's app was being processed applicants were waiting 6 to 9 months for interview dates.
I don't know your relationship profile but I suggest sending more proof of relationship via Case Specific Enquiry. I would also go visit if you can.
There are many threads on the forum to help your wife prepare for an interview that I recommend you search up.
Although rare, it is possible to have the interview cancelled. I've seen two forum members - three if I count myself - successfully have the interview waived after receiving the interview queue letter.
It was a mix of persistence, bombardment of relationship proofs, leaving my job with a nice severance at a very convenient time, moving in with my wife and my in-laws in a remote Indonesian village, and last but not least a very well crafted email addressed to the Risk Assesment Officer and First Secretary of the High Commission of Canada in Singapore that led to a response from him two weeks later that he personally reviewed and approved our application. We were told we were approved while MyCIC still said that the background check and final decision hadn't been started and two days later we received PPR.
Good luck with your app.