One source that was briefed on the new OM 150-600mm 5.0-6.3 lens told me this:
150-600mm (not a pro lens) with stabilization co-work with camera body. I believe the telephoto lens is sigma designed and manufactured from their existing full frame 150-600mm. Weight is 2+ kg.
It would be disappointing if this would be EXACTLY the same lens. This lens was designed for FF and it would be unnecessarily bigger than it should. SO I hope that if it is based on the existing Sigma it might have been optically adapter to MFT.
Hope sources can soon confirm (or debunk) this rumor…