I have no doubt that toy comapnies have already considered this product. If, based on market research, it seemed to be a profitable endevour, they would be offered to the public, but clearly, the demand is just not there.
While I agree that "times are changing" and some men are assuming a greater responsiblity for caring for their children, I do think there is an inherent difference in the way boys and girls like to play (generally speaking). I honestly didn't believe this was the case until having children of my own.
For example, I have 17 month old twin boys and my best friend has a girl who is 16 months. Our toddlers play together all the time and they are always exposed to each other's toys (ie: traditional "girl" and "boy" toys). My friend's daughter is very eager to sit and feed her baby doll; my boys, on the other hand, can't wait to get their hands on the baby just so they can throw it across the room.
If one of my boys ever expressed interest in a doll, then no problem...we'd get him a doll. I think this issue has less to do with societal stigma and more to do with demand for the product.