They need is Ana C and a backup libero, Julia B and Diana to be better next year
More than this, I would add an OPP. As many have already pointed it out, Brazil lacks of a decent+ OPP since Sheilla retired. Tandara was okish from time to time, but Brazilian's play game has never been one-player based. They rely a lot in the distrubition to all their attackers (Does someone remember a Brazilian player being the top scorer of a tournament? Usually not).
Even if Julia B and Diana improves, the abscence of an OPP will haunt them. Especially in the vball which is played now.