The question of whether your wife will "let" you shave your chest hair, or if she is "asking" you to keep it because it helps her feel that you are still her man is debatable.
Often when people describe issues in a hurry, they don't pay too much attention to the precise meaning of the words they use, and also they do post from their own point of view and not their partners. This is why any discussion on "letting" vs. "asking" from other members here is counter productive. It also doesn't address the issue you would like resolved. And, as much as we like to believe that we should all have full control over our own bodies, the question of male feminization is NOT the same as whether either partner should choose to get a haircut or put on weight, since the haircuts and the weight are every day, garden variety options. Male feminization is not and it behooves both partners who are in a relationship together, to discuss this.
At any rate, the importance is that you are both talking about it, I assume in a spirit to come to a meeting of the minds.
I can tell you how my SO approached this. First, she didn't ask, she just did it, and I assumed that she didn't consider that I would have an opinion either way. This hurt a little but I didn't say anything since it was water under the bridge and I got over it. Second, she goes out frequently in the mainstream and in the summer time the tops show more of her upper chest and back than do men's clothing. So as with the legs, in our case it did make sense that she would want to shave in order to not attract undue attention to herself while going out. She then told me, and it makes sense, that it is much easier to keep it up throughout the year since it is quite time consuming to have to shave an area that hasn't been shaved in quite some months. My SO also has a lot of body hair. So .. the shaving is not an issue for me even though I also enjoy male chest hair. I also consider her need to present femme convincingly of prime importance.
My SO doesn't tend to focus the crossdressing on bedroom lingerie though, even though once in a while she'll wear lingerie. But, if her focus was on this and she wanted to shave her body because she felt the body hair looks unsightly (as opposed to the more utilitarian reason of shaving it in order to present in public more convincingly), I'd wonder if she was developing a degree of Gender Identity Disorder (GID), and if this might be an indication of a future pathway to wanting to alter her body in other ways or eventually live as a woman full time. Not saying that having GID is bad, just that it needs to be considered.
This could be your wife's larger concern and if it is, I don't know what to suggest. If she begins to believe that you feel as a woman internally and this is something that is always present as opposed to a desire to present as a woman occasionally, the two of you have more to talk about than whether you shave your chest or not. There is a possibility your wife will be turned off in the bedroom if she is not keen on having a relationship with another woman? I don't know this, you should ask her.
I don't know your wife or her motives and I can't be of more help with regards to your decision to shave or not to shave, but hopefully I've given you something to consider.
Originally Posted by ReineD
...) and maybe she's associating the chest hair with something else. However, I would NOT advise you to shave it without talking to your wife. Knowing that this isn't something she wants, or isn't comfortable with just yet, would deftinitely be hurtful to her if you did it anyways. Good luck!
anyway. 
