Regarding the weird boxy shape seen on the 055 under construction or the "hole" for the gun seen in satellite pictures, these prove nothing.
First, the weapons are only fitted after the hull is complete. There is close to zero probability that the rectangular object on the first 055's foredeck is a gun mount of any type, because the hull hasn't even been assembled! This is no indication that the Type 055 will have an enclosed gun mount.
Second, a square or rectangular barbette is physically impossible. For something to be able to rotate like a gun turret, the base must be round, and only the rotating part above the hull can be rectangular. As such, the rectangular hole proves nothing either. For all we know it could be a rectangular ammo handling bay for a round turret!
Yes, the possibility exists that the 055 might have an enclosed gun mount. However, so far, there is not a shred of evidence in the 055's construction that tells us what kind of gun mount it will have. For now, there is sinply no way of knowing.