I think I've had enough time to experience and get a good feel for 1.3 by this point to reevaluate my
previous analysis on which Update was the most important. I still stand by how 1.2 was the most important Update. I still think 1.3 was a very great and important Update as well, for adding an Endgame Event, Final Boss, New Difficulty Mode, and making old elements of the game become much fresher (New sprites for old Ores, Updated Goblin Invasion, Revamped King Slime with a new event dedicated to it, better player customization, and new Mini Boss enemies for the Underground Corruption/Hallow) along with signifying Redigit's last update on Terraria before he moved on to other projects.
Still 1.2 represented the "revival" of Terraria with 1.3 sort of being an extension of 1.2 since they planned to add the final "Lunar Boss" back in 1.2, but this eventually evolved into the Lunar Events we see in 1.3 which required it's own major update. Terraria could've ended at 1.1, and it was planned to end it at that update because Redigit was facing real life/personal issues. It was certainly still a complete game on it's own, it would still have been a great game that can give many hours of enjoyment beyond 1 Playthrough, but it still felt like something was missing, which is why Terraria wouldn't have the same level of excitement in the long run if it didn't get the 1.2 Update. 1.2 added tons of new Furniture, the Dye System, expanded the Ice Biome, and was able to bring Hardmode Content to every biome in the game to truly make the 2nd Half of the game feel complete. Overall, it feels like 1.2 was able to fill in something that felt missing from 1.1 and 1.3 helped 1.2 to make Terraria become truly complete.
Now about the future:
Assuming the
New Event Cenx mentioned was not an April Fool's Prank I am curious to what it could be, and what "Tier" it would be in. Since 1.3.1 sounds mainly focused on adding new mechanisms for the builders of Terraria, it never even crossed my mind that something somewhat big as a new Event would be added for this update. Even though I know 1.3.1 probably won't just be about wiring.
I'm still assuming that it was part of the April Fool's Prank, but knowing Re-Logic in the past, part of their April Fool's pranks turn out to be true. (Not the whole thing, but part of them with Duke Fishron and Martian Madness being examples). And it's very unlikely they would actually remove the Rod of Discord from the game. Either way this could be one of many surprises that many people weren't expecting to see on this next update.