>>57330126What it should've lead to: BDSP, but properly reworked for Gen 8, 2021. Includes Platinum content, Gen 8 redesigns for the characters, Origin Dialga and Palkia, Dynamax, Sinnohan Regional Variants, connectivity to SWSH with a patch to SWSH for BDSP compatibility, and a postgame episode that teases PLA and hints at DPPt being an alternate universe.
What most of the fanbase says it leads to: Platinum because it has the most complete Sinnoh story.
What it actually leads to: BDSP. BDSP's Azure Flute is linked to PLA's. PLA's protagonist also has a smartphone with a more modern design (no physical buttons below the screen), making it very unlikely to impossible for PLA to be directly linked to Gen 4 Sinnoh.
The Arc Phone was a mistake. 
