CodeGlue will also remain on board for any future 3DS updates.
I spoke to CodeGlue on their discord yesterday. They said:
"Unfortunately we don't work on it anymore

So we don't have any knowledge about new patches or anything
Sorry!"
From this information, a number of conclusions can be reached.
1) The 3DS development ended when codeglue lost their contract and we are being ignored.
2) The Terraria developers have not decided if they are going to release another update or not, and so they are not commenting yet.
3) The next patch is being worked on, albeit slowly and cheaply, and so a timeframe for release is nowhere near. <- My guess
Why do I believe this? The PS3, XBOX 360, and WII U are no longer manufactured or distributed. The Vita mostly only sells in japan (15 million sales globally since launch).
Terraria stopped development on these markets since they are obsolete.
The PS4, Xbox One, Switch, and 3ds are all fresh markets. The 3DS has sold a lifetime of 67 million units. That is five times as many as the vita, over twice as many as the xbox one, more than the PS4 lifetime sales (60M). Weekly sales numbers look like:
-----------NA-------EU---------JP-------EARTH
PS4-----78,457--156,182---21,208---331,394
Switch-51,468---43,478----24,821---144,841
XBOX---39,424---26,633----152--------77,502
3DS-----20,972---12,766----15,897----52,093
3DS is a hot piece of hardware. Terraria is a hot game.
FIX THE HOT GAME ON THE HOT CONSOLE