In mid-2017, Re-Logic started work on the "1.3.6" update. We would periodically see spoilers for the next couple years, far longer than a 1.X.X update would normally take. (Usually no more than a year) Then, as the devs release the amount of content they were adding justified a larger version number, in 2019, it was announced as Terraria 1.4 before being released in 2020.

At the start of 2023, Re-Logic announced work had started on the 1.4.5 update. One of the inclusions for this update was the inclusion of upwards of 12 new music tracks by Scott Lloyd Shelly. To accommodate the time this would take him, Re-Logic decided to continue adding features to the game while waiting. To date, for this update, the devs have announced a Dead Cells crossover, a Palworld crossover, 10 new music tracks, new seeds including a skyblock-style challenge, visual overhauls of bosses, new UI, localization for new languages, and many new items and weapons.
By January 2025, it will have been as long since work started on 1.4.5 as it was since work started on 1.3.6 when it was announced the update would become 1.4.

In my personal opinion, this is a weird middle state because it certainly seems too large to be 1.4.5, but the game is also pretty much as complete as it can be. Every 1.X update to date has added new bosses. We haven't seen any indication of that, and the game is at the point where there aren't many points in progression where you could squeeze one in. The only official word we have on the release date is that there will be "no release date announcement ready in 2024", but as of September, they had settled on deciding a final list of content, which to me implies they are wrapping up work. I think it could go either way, but I'm leaning slightly towards a "1.4.5" update with maybe a big name and branding (similar to "Journey's End" for 1.4), so that they can market it as a bigger update.