your wife might end up becoming your husband, if you are ok with it. if you can't stand the thought and are unable to accept, your wife will either stay as your wife, or you will split up. kind of depends on too many factors to know yet.
not all trans men want bottom surgery. there are many different reasons why, for some it might be for the sake of a relationship, for other it's the result that bothers them, as science still can't provide a perfect functional penis for people who lack or have lot one. you should talk a little bit about this, if this is your biggest fear right now.
being open and voicing your concerns without being judgmental of your partner will be important. taking things slowly together, is probably the easiest way for you two to support each other through this ordeal and find an end without too much hurt and heartbreak. transition usually starts with hormone replacement therapy, which results in some features like voice and hair growth changing, as well as the size of the clitoris (it won't grow very big, so that's nothing to be afraid of). another thing that will change is the body odor, it will change from a female to a male scent. the experienced need to change other body parts might also change, so it's worth trying to let things happen and see if you can still maintain the attraction.
people can get a little caught up and start obsessing over transition. they may become wary of others, also their partner, and start doubting their partner's intentions and true feelings. i know a woman who's so started transitioning, with her consent and support, but that relationship isn't going too well because the so doesn't believe in the woman's acceptance. both parts in a relationship will have to be open and honest and make an effort to be understanding of the other, and trying to believe in the other's love.
one thing you should always keep in mind, is that the person will not change. it's only their exterior and the way they express themselves that change through transition, just like how the inhabitants of a house will still be the same people even after they renovate the house so they can live more comfortably in it.
though i can imagine this might get really difficult if you have no attraction towards men whatsoever.
come by with all kinds of questions whenever you feel like you need answers from someone else than just your partner.