I'm not exactly sure what the release scheme for Delta Rune will be, it's still not even entirely certain whether the game will be released but it is looking more likely than when the demo just came out and Toby Fox was very reserved about confirming it'll definitely get a full release.

Everything points to the game being structured as a sequence of seven chapters, each consisting of one in-game day, leading up to a climax. The first chapter/day has been released as a free demo, but looking at an old interview it seems the remaining chapters will all launch at the same time.

Undertale did something similar, the game's split into very clearly delineated chunks, and the free demo was the first chunk of the game. Having played both myself, I can confirm that not that much actually changed between the demo and the release version of that chunk.

There do seem to be some JRPGs that try to be more focused around characters, I think Persona is often mentioned, though I've never played them myself. It's a shame that a genre so lauded for its epic plots so often have rather barren stories to tell, but maybe we've not been playing the right JRPGs!