I think the Hedgehog Engine is great and they shouldn't ditch the tech... While Unreal is good it's only free until you sell a certain number of units then you're handing over a percentage to Epic Games... Instead I think SEGA should set about building their own multipurpose engine for all internal developer to use. (SEGA West or Japan I don't care.)
I don't think the Hedgehog Engine is great and when you compare it to Unreal Engine 4 it's no contest, the price you save on R&D is no small sum Ryan. Think about it, Shenmue 3 is entirely possible because of Unreal Engine 4, if Suzuki had to develop his own engine that dream would have escaped his grasp.
And it's not just the smaller developers either, Square Enix is happy to use that engine to develop Kingdom Hearts 3 and it's not just them, Namco's using it for Tekken 7, Microsoft has several titles using it and Capcom's using it to make Street Fighter V. You should keep in mind they all have their own inhouse engines and yet they're all flocking to power their game via UE4, it's a ringing endorsement.
So if all the big boys are using Epic to help deliver their game, it's surely a good idea for SEGA to jump on board.