That's the sad truth and reality about technology. It's an escalator, not a staircase. It moves whether or not you want to move with it...you can try to walk the opposite direction, but you won't always get too far. At some point you will need to just embrace the advances, and at some point things will hit a technological wall.
Technology is ever evolving, and ever advancing. Technology cannot infinitely expand within a box, eventually it needs a larger box. By confining technology to a smaller box, we're directly limiting its growth and expansion, which is, for the most part, the case behind console Terraria. Terraria already has a ton of coding wizardry that allow it to function in its current state on old-gen...but the fact of the matter is that Terraria has grown to the point where it needs a bigger box. It's sad, but it's true.
Sticking too long to outdated / older / less modern technology will halt the further advances of technology to newer and higher levels. I wish it weren't the case, since I can completely relate to the issues of "I can't afford a current-gen console" or "I already have the game on 360, but it's not getting any support." I sympathize with this, entirely. But Terraria is just at its limits with how last-gen consoles can interpret and support the game. The game itself gets bigger and better with each update, but 360 and PS3 don't.
That being said, I do sympathize with the issues that might prevent users from being able to upgrade to a PS4 or X-box One, just not much can be done beyond the large amount that has already been done to put Terraria, in its current form, on 360 and PS3. Eventually you just hit the wall.