It looks like the “climactic story event” will be a part of, if not the whole of, the New Republic theatrical film:

A ‘New Republic’ era film (live action movie by Dave Filoni) - a general discussion thread

I do wonder if rumours that season 4 of The Mandalorian will contain rewritten and adapted scripts or stories from the now cancelled Rangers of the New Republic series.

On the official announcement for Rangers of the New Republic, was this description:

“Set within the timeline of The Mandalorian, this new live-action series from executive producers Jon Favreau and Dave Filoni will intersect with future stories and culminate into a climactic story event.”

Personally I think it is a bit shit we’ll have to go to the cinema and pay for tickets to see a possible finale for the various Mandoverse TV series that “culminate into a climactic story event”. Or wait a number of months until the New Republic film appears on Disney+.

That, and do I do hope they land this New Republic film, and whatever this “climactic story event” is. But that hope is fading if the quality and execution of stories is going to be like BoBF or the last season and a half of The Mandalorian.