@v48e12 There won't be any structural physics. You will be able to create crazy and impossible builds in the new version as in the old one. As red said they want to transport the same mechanics over to the new engine first.
The reason why you may want to use a modern engine is because it implements all aspects of a game inside one complete solution. That implies graphics, animation, sound, textures, shader, physics.
The game and its mechanics will be the same. The only differences will be the way higher level of graphic quality, overall performance (A performance you will never reach with Java) and the ease for Red to implement new things.
Regarding consols. Hmm yeah maybe not that many people would play it on a console comparing to PC platforms. But there are console player out there playing such games like MC. So why not?