Hi, Krista.
I think all of us who transition later in life, with a spouse, encounter this situation at some point. Not everyone needs to transition. You will have to chart a course, with the help of your therapist, that will work for you.
Can you live with keeping your trans-ness secret from everyone forever? For me, the answer was clearly no, and that is what drove me to come out to my wife, whatever the consequences. I looked ahead to see what my life would be like if I continued on the road I was on, and frankly, it scared the crap out of me. I saw in my future only misery, depression, and a very bad end. I knew that I had to change the direction of my life in order to survive. If that describes you, then you have to come out. If your future looks to be unfolding differently, then you have other options.
People might reject you; it happens. You might find that it is fewer than you think. When I came out in my community, I was prepared for some redneck opposition. I found none at all. Similarly, on Facebook, I was expecting to lose some "friends". In fact, I lost none, and the number of my "friends" doubled.
You will find yourself in the position of unwilling educator. Make the most of it. You won't be able to reach everyone, but you can often correct misunderstandings before they evolve into hatred. Most hatred starts as ignorance, like the belief that trans = gay.
Early on, my wife asked, "Does this mean you are gay?" I said, "No, it means I am lesbian." That helped reassure her I wasn't going anywhere. And one of the first things I said to her in our coming-out conversation was, "I have no plans to leave you."
If you decide to come out to your wife, the ball is then in her court. If she sticks with you, you will have the best ally in the world. If she doesn't, well, you won't be able to stop her. Scary AF, I know, to think about those possibilities, but that's why you need to visualise what the future would be if you didn't come out, like I said above.
Whatever you decide to do, you will have support here. Good luck in planning your future.