@Background Pony  
More like a village  

Hasbro DOES own all of Sunbow’s library now (Sunbow being the company that made the G1 MLP, G.I. Joe, TF, and Jem cartoons). However, I personally do not believe a Rainbow pony themed special was ever intended to be made. Little animation clips were often made for G1 commercials. I think the clip in question was just a quick advertisement for the Rainbow ponies, tacked on to the end of RaMC (on some VHS tapes.)

@Beau Skunky  
I’m the personification ponification of the spectrum of light. Rainbows are cool now. :D

@thps48  
Yeah, you have a point. I forgot about the legal issues.
 
Though, on the other hand I’m kinda glad FireFly got retooled into “Rainbow Dash.” (It sounds kinda like a tomboy-character name to.) Otherwise we wouldn’t have “Sonic Rainbooms,” and she made rainbows “cool” again.

@Beau Skunky  
My understanding, and it’s not all that much lol, is that TMNT’s owners retained everything in their copyrights, then gave Nick those rights in exchange for royalties. However, MLP got some corporate suckhead involved and they needed to remake G3 or G1.5 from scratch, ergo G4 gets rehashes of the newer generation ‘cause it can’t use the older generation from Faust’s childhood. I assume, yet know not the whole picture, all rights were handed over to what’s-it’s-name excluding Spike, Applejack, and the theme, so that’d mean they’d own everypony else from G1 including the non-ponies. Like Geno, there’s probably some sticky situation involved in legal that prevents a reappearance (or they didn’t have the funds, as indicated by the cheap-o nature of the merchandise up until G4 burst the franchise back to life.)
 
tl;dr? Legal bollocks runaround makes cameos harder, but does nothing to prevent homages.
 
Again, if Rainbow Power bears no legal obligation with the company I somehow never learned the name of these three years, lolwut?, then it should work out fine. :3

@thps48  
Y’know, I actually wouldn’t mind some of the G1 villains coming back, or perhaps new versions of them like how they’re doing new-yet-familiar versions of the TMNT villains in the new TMNT series. (The Rat King got a really creepy make-over.)

So, if the buyers of G1 didn’t have knowledge of Rainbow Power, this mean Hasbro has the ability to air a Rainbow Power two-parter?
 
Hopefully, we also get that Quest of the Six Princesses remake I’ve been wishing for ever since Skyla, and a Katrina homage. I chose her for my wish list partly ‘cause it’s tangentially related to Rainbow Power, but mostly ’cause it was fresh in my mind after reading the above article. <.<;

@Itsthinking  
That’s what I meant. If they did, they would have done it by now because that was the original idea.

@AntarcticRainbow  
They can’t bring G1 to G4. They don’t own most of it.

Honestly, it’s not going to be the special. It’ll be it’s own thing. If Hasbro was going to bring in G1 to G4 they would have done it before with Lauren’s initial designs of the mane six.

@Tenafly Viper  
It’s possible a nod/revival, but I think it’s a coincidence personally.
 
Still, it likely won’t have any effect on the canon of the show, like those “giant” TMNT action figures don’t have effect on the new TMNT show. It’s just a “new look” for the toys.

@Background Pony  
I think OP is just noting the correlation between the G1 rainbow ponies, and the upcoming rainbow line. It seems to be kind of a nod to the history of the toy line.

Am I the only one who lul’d at seeing the “Doctor,” and DJ as part of this new toy line? I gatta say I like their “rainbowy” looks.
 
@Background Pony  
Not every toy-line gimmick gets an episode, or anything. I’m still waiting for Applejack’s truck, Cadance’s baby, or those pony “Mexican-wrestling”-like masks to make it into the show to.
 
Still, if it does, I imagine it might focus on Rainbow Dash somehow.

OuO

Rainbow ponies have existed for years, and there were several G1 toy sets of them.
 
But I doubt OP knows that and probably just assumes they don’t.

Crystal empire all over again?
 
Rainbow empire
 
Rainbow dash for the next princess

Winged version of Spike? Weird.

A coincidence, I’m sure.