Going x86, wont magically give us a wide range of hardware to run on, it won't port new software, it won't expand the userbase..
It would provide a cheaper platform, even if it was only a single specific motherboard that was supported.
The barrier to entry for people interested in giving AmigaOS4 a try is MASSIVE. It's for the hardcore users only at the moment. These users are important, it's true, but they're a tiny market.
Would it grow the userbase? Well, at a reasonable price for an x86-64 (or ARM) version I'm sure it would sell quite a lot to people who are interested in the Amiga still (ex users in the main) but who don't want to put down the better part of a grand or two for the computer to go with it.
But yes, there wouldn't be any x86-64 (or ARM) AmigaOS software to run on it, it would all need to be recompiled, which given the quantity of abandonware on the Amiga would be difficult. Libraries using PowerPC assembler would also need some effort put in to optimise the x86/ARM path over the default C path (if it even exists).
To artificially impose barriers on your market is a terrible business plan, and bespoke custom PowerPC boards that cost 5x as much as an x86 board, and 10x as much as an entire ARM system, are a massive barrier. No, it wouldn't make AmigaOS rocket up to being a major OS player, but it could double or triple the userbase - possibly even ten to hundred times the users if a Raspberry Pi, or ODROID-XU version was made.
I on the other hand, do not mind paying for hardware and software.
Whoopee for you.