I was scrounging around and found this for sale on Ebay from SPGGY.  He claims he got it from an inside source at HASBRO.  It said something like how it was a prototype that Ben Yee got a hold of, that he bought.  HASBRO said something like they were planning on pulling the project for a later release.  Ben Yee of BWTF.com has a review for the toy for sale below:

Supreme Megatron:
Current Bid: $83.00

Review:
In the BM show, Megatron built an entirely technological head to house his spark.  It was to be his last resort to purging the organics from his body.  The head floated about Cybertropolis like a mountain.  The head towered over many of the buildings, looming over the Maximals powerfully.  Now comes the toy.

For all those Megatron fans out there that were dissapointed with the BM Mega Megatron, don't fret.  Now comes Supreme Megatron.  You thought Cheetor was big?  Well Megatron's giant head takes up the entire Supreme box, give or a take a few inches.  The toy comes to about a foot and a half.  Pretty decent considering he's the FIRST BM toy to be proportional.  But let's take a close look at HASBRO's latest opus.

Robot Mode:
In robot mode, Megatron strikes the god-like appearance of a giant head.  In the TV show, he floats around Cybertropolis, looming over the Maximals at every corner.

The head, on the other hand, lacks the intimidation of it's TV counterpart.  His dominant colors are purple (leaning more to pink), white, and a dab of vacumed metallic orange.  The large eyes strike a powerful red.  But, by triggering a special tab, you can activate a color change.  Megatron's eyes change from sinister red to fiery orange!  Although not much is noticable int eh color change, the light inside does turn on, giving him a 'fiery stare', or so the box calls it.

Only draw backs are the color changes, mainly from a bluish purple to a pinkish one.  Another problem is the apparently usless eye color change.  Sound of a laser would have done better.  But HASBRO doesn't always give us what we want.

Vehicle Mode:
In vehicle mode, Megatron is a powerful space shuttle/ship.  The ship resembles the one the Predacons rode during the Beast Wars.  Although this mode was seen only once in the show, I looked forward to it.  The vehicle mode is highly underated.  The ship mode is pure G1 classic power.  Transformation is quite difficult, starting with splitting Meggy's face in half.  Be warned, though, the vaccumized metal on the eye brows easily chip off in this process.

Finally, after a 10 minute transformation, Megatron is in the ship mode.  The first thing you'll notice is that it is quite funny looking.  It holds no cockpit or control center.  A front is quite obvious, though.  Two large 'jet thrusters' rest in the lower back of the ship.  The thrusters easily light up with a press of a button on Meggy's head.  A ncie gimmick is the fact that the thrusters are holes as well.  You get two large lasers two plug in there to 'fire out at Maximals'.  But I prefer to think they are jet exhaust coming out.  The light shines easily through the translucent plastic missiles, giving it an Optimal Optimus look.

The box claimed to have an easy lock postion, but the missiles kept firing out when left alone.  HASBRO said it was a glitch in my toy, but isn't that what they said about a certain Prime's chest area?  Na, mine must have been loose.  Either that, or it's a toy that can rival Powermaster Prime at an eye poking contest.  But I guess it was just my model.

Drawbacks are minmal. The fact that it holds a G1 feel shadows the complaints.  First, the color scheme is basically the same.  My little brother also had a hard time telling the difference of the Vehicle mode and Robot mode becasue of this.  No guns are also found on this vehicle mode.  The back thruster rockets are a lame excuse for weapons. A fusion cannon or something would've been more exciting than tiny little laser missiles (pointing ot the back, no less).  Also, a section of the back of the head (about the size of a cube of Tankorr)does not move.  This provides the look that not much changed in the back section of the head.  Oddly enough, there's a logical reason for this.

Playset Mode:
Megatron actually has three modes.  His third mode is a 'playset', considering his size.  The back section of the head can open up, revealing a main chamber where a transparent plastic/crystal pilar rests.  Suspended in the center of the pilar is a red Megatron 'code' head.  It is done the same way as the spark crystals, except on a larger scale.  The coding face is about the size of BM Blackarachnia's head.  A single tentacle is accessible, but is hard to reach due to the lack of space.  The chamber is rather small, only able to houde a single deluxe toy at a time.  This is due to the transforming parts.

My few regrets are minimal.  Adding a third mode to this character is coming near to its due.  The size of the chamber is rather small, though.  Thrust can fit, but basically takes up the entire chamber.  I have found only Obsidian and the other basic generals to fit easily and can still move in the tiny chamber.  Also, the chamber is quite tight.  Don't expect retrieiving Tankorr's missile will be easy.  I'd suggest a screwdriver.  It took me almost an entire BW show to save Jetstorm's missile.  The tentacle in the chamber is also close to impossible to control.  If they had only put a magnet or something on it, then it would be of use.  It seems to just take up needed space.

A good point to this mode is the code face.  It keeps the detail of the show, but to a minimum.

Overall, the Supreme Megatron is quite impressive.  The lack of complex transformation is a dissapointment.  But, for a transformer the size of a house cat, and it basically takes the whole box too, it is good enough.  I guess it would be even more of a dissapoinment if he took an hour to transform to a mode that barely looks different.  I also wish they loaded in more lights.  A light in Megatron's chamber would have been nice.  Seeing that code face glow would've given me the chills.  Unlike Supreme Cheetor, Megatron is worth your $40.  It keeps the authenticity of the show and adds a little spice of its own.  This toy requires a pair of AA batteries.  Overall rating: A+.