I don't think this would be very possible. A LOT of things are apparently changing in 1.4. I feel like adding only a few more items and nothing else would imbalance things, in a sense. What if a new item is only useful in a new minibiome they're adding? Or only craftable through some new method? I doubt there's a ton of new items that would be available and make sense using only the features 1.3.6 has.
Plus, then there would be another update every month. The devs would have to go take the time to create a separate 'full version' of Terraria (and have to extract ONLY the items they've chosen to add from the 1.4 version and transfer it into the 1.3.6 version- I'm not a game dev, so I don't know
how hard that would be, but it sounds like it could be potentially troublesome imo). Then, they'd have to stop every month and fix tiny little bugs those 10 new items could cause- instead of doing bug testing on the whole of 1.4, all at once. It's generally more work overall, which would lead to 1.4 being pushed back
even further- and isn't that the whole problem in the first place?
In general, I don't see why this delay is such a horrible thing. Sure, Re-Logic doesn't have the best track record when it comes to releasing on time. But you aren't behind the developments- you can't say you know what happened. It could have been a perfectly good reason as to why they had to delay. Hell, they could've given themselves a ton of wiggle room for all we know. But maybe one major, unexpected bug came up and took up a lot of that time. Then another popped up- and suddenly all their extra time is gone. They thought everything was going under control, but now it's impossible to get everything done well before December, so they have no choice to postpone the update. Or, they might've underestimated the time on purpose, sort of 'wishful thinking', to keep the community for screeching at them for daring to announce a 2025 release. Or, maybe they did just underestimate how long this project would take to complete, like they have many times in the past. There's no telling. But if they're behind on development, I feel postponing it is crucial to Terraria's success going forward- many of you are already sick and tired of waiting. After the delay, many of you are saying that "it'd better be a flawless update for this". And that's exactly why they had to delay; after all this time with no updates, the community is going to expect a perfect (or near-perfect) update. So, to meet that expectation and satisfy their fans, they have to make sure they're able to deliver the best update they can. Plus, Re-Logic has always seemed to put quality first, even if that sacrifices some of time and customers' patience.
You all have a right to be upset- mad, even- but this mistake could have happened so easily for so many reasons, and I'm kinda surprised none of you are even seem to consider that. The amount of negativity these guys are receiving for such a human mistake blows me away.
I wish Re-Logic best of luck in finishing 1.4. Even with just the minor spoilers we've received, I'm sure the update will be well worth the wait. I mean, I'd wait 3 years for a cool new duck.