When Jobs came back Apple stopped being beige and started producing fun, quirky, colourful computers with iconic visual design. Jobs didn't try to re-release the Apple Mac - he tried to produce a product that had the USP of the original Mac, but with newer technology and better design.
A successful Amiga reboot would have to reinvent the Amiga difference and not just produce something average that happens to run AmigaOS. You'd have to introduce technology maybe five years ahead of the market mainstream and dramatise it with show-stealingly awesome demos.
That's a hard thing to do in 2015 - possibly harder than it was in 1985 - and anyone planning to do it probably won't be aiming at any of the current computing form factors.