Yeah it hasn't been announced yet I know. But a few days ago my school club senior told me that he obtained some commercial secret implying that BT09 will have Murakumo and Aqua Force. He added that Bushiroad seems to be considering whether to include Nubatama or not. Aqua Force is a new clan and it's also time for upgrades to Murakumo. My guess for why Nubatama is put into consideration is because it is too popular as a clan and Bushiroad may do it in the form of fan service. I also predict that Gold Paladin will be coming so as to complete the line-up for the 7 Sacred Beast Armour wearers, Narukami for more builds and possibly a new clan in Star Gate since it has only 2 clans.
Just take these as a grain of salt. With most of the BT08 revealed, it would not take long for BT09 to be announced as I don't really trust my senior.