A very small, blurry photo from a Japanese display somewhere (source of the display/convention is not known), shows us some upcoming redeco figures for the JP Arms Micron line, including a white & red Thundertron, noted as being Leo Prime.
Not sure if the name is being read from the display cards (by whomever took the photos), as the name Leo Prime was floating around at the time Thundertron was first revealed at a JP convention... so either it is actual name of this redeco and the names were just mixed up by accident, or the name isn't applicable to either and someone is just guessing with a name that was already out there.

Either way, it could end up being another JP exclusive, as Hasbro seems to have stalled on their future TFPrime toy releases, with TakaraTomy powering ahead with a lot more moulds and redecos.

The news article also lists the upcoming Arms Micron numbers, if they were taken from the info cards and not just guessed by someone later.

AM-21 Arms Master Optimus Prime (new for AM)
AM-22 Dreadwing (redeco)
AM-23 Wheeljack (new)
AM-24 Silas Breakdown (redeco)
AM-25 Nemesis Prime (redeco)
AM-27 Ultra Magnus (new)
AM-28 Leo Prime (redeco)
AM-29 Shockwave (new)