I'll be painfully honest. An incredibly small percentage of us end up staying with our spouse. As you said, it's difficult on your wife, and it was much the same for my JoAnn. It took two years for us to accept becoming "Friends". And for a short time now we've even come to terms with being nothing more than roomates in the house my wife will soon fully own. However, most wives never even remain our friends, and as couples we have to realize that before healing the wounds. JoAnn and I understand our separate lives now, and we aren't afraid to talk about what we're planning.
I personally know one couple in Michigan who stayed married, but as tremendously loving friends. While I know two couples that found transition brought them closer, and allowed them to expand their life experience here here in the SF Bay Area. But those are the only three couples I know who stayed together, and that's from more than a hundred previously married (or coupled) transwomen and men that I know and occasionally talk with.
No, the odds of staying together aren't good, but that doesn't mean for you to give up on marriage and run. You could be part of that small percent of couples that finds a peaceful and loving reationship. As many of us have said before, "Hope for the best, but prepare for the worst." It's good advice, even if it's a terrible thing to hear.
Katherine