SEGA revealed that will announce a new Role playing game to TGS 2021. He did so in the description of his stream on the event streams page. Unfortunately, he did not provide any details on this, so it is difficult even to speculate. The only certainty is that it shouldn’t be an Atlus title, because the company isn’t mentioned in that particular line.
Whether it’s a new Sakura Wars or another Phantasy Star? Maybe a Shining Force? Of course we are making random hypotheses, also because it is not possible to do anything else. In reality, the possibility of a new Sakura Wars is more concrete than the others, because on the site of the Tokyo Game Show 2021 the 25th anniversary logo of the series appears. However that may be, you can never tell. It could also be Valkyria Revolution 2, for all we know. To find out, we just have to wait for the event.