Found out some very cool information that might be of interest, since I didn't see it documented.
As a matter of fact, it does turn out that the Elemental Knights were going to be released in the US! Boxes for them exist, and I've got a few photos as well!
Apparently, in South Korea, the Elemental Knights, and some other products, were released using repurposed Japanese and American/Canadian boxes, which had international stickers applied. I assume that they were either scarcely or completely unreleased in the US, as I've never seen one show up, however, the box style matches if you remove the stickers. They were referred to as "Tenkai Elemental (name here)" on the box. Robofusions did actually exist for the Accelerstrike and the Valorn/Lydendor one, and that beast figure apparently must have seen a release somewhere! I've found boxes for Braven, Tributon, Beag, and Valorn. Lydendor and the Beast World character are nowhere to be seen from my research, but they exist out there somewhere. I did attempt to find Dromus's elemental form, as well as Neo Vilius, but I didn't have any luck. I'm assuming since the wave already had 2 Robofusions with 3 characters each, that Dromus and Neo Vilius would have been saved for a theoretical fourth wave that was never produced. It's also worth mentioning that these releases of the characters do include the Robofusion pieces, whereas the Japanese releases did not. Makes you wonder what we could have seen in Wave 4. Elemental Dromus, Venetta, and Elemental Vilius sounds like a safe bet to me! If that wave had existed, it could have contained the second half of the Beast World Robofusions that never saw the light of day!
I thought it was really cool to finally find out that these were in fact produced for the American/Canadian market, as I had thought for all these years that the US was just never planned to get them due to cancellation, but it seems it was just funky distribution, and chances are leftover US stock got sent overseas to be repurposed in Korea.
So, there you have it, for anyone who was ever curious, like I was!