None. We don't need any more. We do need to see some consolidation and diversification of the factions we already have.
I don't get how
BT get rolled into vanilla while
BA,
DA and
SW still retain their own separate books... if non-codex Marines can go into Codex: Marines, they
all can. Failing that, have one main book for codex chapters, and a smaller one for all non-codex chapters, restoring all their fluff, rules, characters and units that actually differentiate them from vanilla marines, otherwise why bother? Why this half-and-half effort?
Daemons, Traitor Marines and Renegades (
LotD) go into one big Chaos book. Sisters, Deathwatch, Grey Knights and forces of the Inquisition go into another, possibly an AdMech supplement could go here, making a sort of "Imperial Support/Allies" collection.
Imperial Guard get expanded with new regiments, starting with the old metal ranges getting plastic updates so not restricted to Cadian/Catachan ranges. The Guard range has a fraction of diversity compared to Marines, where they should have at least
twice the diversity.
Tyranids stay. Getting rid of an entire faction now makes even less sense than adding new ones. Not liking their models or fluff is entirely subjective, wanting them abolished from the hobby because of this is rather petulant.