Kingdom Hearts Melody of Memory may be in its final stages of development already. Madison Davenport posted an update earlier this month to her Instagram account that revealed she was doing voice-over work while in quarantine. Naturally, she didn't reveal what for, but it's highly likely that it's for Melody of Memory.
Madison Davenport voiced the "Nameless Star" that Sora talked to in Kingdom Hearts 3 when he found himself in The Final World. Nameless Star and Namine's star were the only two in The Final World with voice over work done for them, implying that the character behind Davenport's star would play a larger role in the future of the series.
Kairi and Riku run across a similar star in the Kingdom Hearts Melody of Memory trailer. Since Namine left The Final World and returned to a physical form at the end of Kingdom Hearts 3, the only star left of importance that Kairi and Riku could be talking to would have to be Davenport's.
Of course, Madison Davenport could be recording for something else entirely, but aside from the mentioned information, there are other reasons that it's likely for Melody of Memory. Through the game's announcement trailer, Square Enix said Melody of Memory would release this year for the PlayStation 4 and Xbox One.
However, the PS5 and Xbox Series X also release this year, so to avoid having attention taken away from the game, Square will want to release Melody of Memory before those consoles come out. The PS5 and Xbox Series X release during the holiday season, so around November and December. This gives Square Enix between next month and October to release Melody of Memory, which lines up the timing between Davenport recording and Melody of Memory being within its final stages of production.
The director behind the Kingdom Hearts series, Tetsuya Nomura, said in an interview with Dengeki PlayStation last year that the next time Nameless Star appeared, she would have her identity revealed. Again — considering the game's announcement trailer — Melody of Memory looks like this is where that next appearance will be.
As to who Davenport's character is, Nomura said in the same Dengeki interview that she's already appeared in the series and the Kingdom Hearts 3 Re: Mind secret boss fight implies it's the unnamed woman from the Verom Rex commercial Sora witnessed during Toy Box. As it stands, fans will just have to wait and see when Melody of Memory releases in the coming months.
Kingdom Hearts: Melody of Memory will launch in 2020 for PC, PS4, and Xbox One.