I agree with all the other ladies, just go in with an open mind and find a dress you feel beautiful in! Months after I bought my dress, I panicked, thinking my FI would hate my dress. He likes to see me dressed up (which isn't very often!) and often helps me pick things out, so he's been a little stressed over not seeing my dress. But he finally told me it wasn't that he didn't think he'd like my choice, he just can't wait so long to see it! We did go to a wedding dress fashion show last week and it turns out, most of the dresses he liked are very similar to mine, so I feel much better!
Your FI will think you're beautiful no matter what, so choose a dress you feel confident in! And if you pick a v-neck dress, he'll probably have forgotten he even said that! LOL