That is not how computer systems evolve, constantly trying to refine old hardware platforms.
Instead new ideas are added in that improve the product.
Look at the Mac, not 68K based, not PPC based, now X64 based.
PPC was not capable enough for the Mac but it is a better evolution for the Amiga? Is Mac ending up back with CISC a new idea? If the Amiga breaks enough compatibility by switching processors, will it have more development after than before? Do we have enough resources to create a whole new AmigaOS with SMP and 64 bit addressing like Mac while breaking compatibility? Is the path forward always easier than the path backward, even while leaving everything you started with behind?
Further, the 68K and the Amiga chipset are both so dated that no matter how much you try to supplement them they will still be somewhat archaic.
How old are the x86 and ARM? The 68k can evolve easier than both of these processors. The 68k support is what is dated but this is due to lack of popular new 68k hardware. The 68k is a loved processor because it is simple and unique. The Amiga custom hardware is simple and flexible which can be expanded. The new Amiga FPGA hardware already shows how fast the Amiga's simple logic can be using more modern technology. Standard integrated hardware which allows for efficient software could close some of the gap in performance with commodity hardware. Consoles are usually not as far behind in performance as would be expected by their hardware for this reason. Jay Miner created a game computer which was more expandable than the game console which the investors expected. A retro game computer is what I would target as well. The market is missing good retro hardware which is more expandable than the Raspberry Pi and more open than the modern consoles with a price in between the two.
AND some of those people you have mentioned have strung the community along for years.
When is the Natami going to be released?
Probably at the same time as the SharkPPC and the new improved version of WarpOS.
Finally, do you really think that new ASICs are going to be created to carry on the legacy of...well legacy hardware?
It is difficult for individuals to create a Natami. I believe the Natami concept was close though. The Amiga PPC boards are lucky to sell a few thousand boards while the Natami bringup thread has 730792 views.
http://www.natami.net/knowledge.php?b=1¬e=33366This makes me think that the AmigaNG PPC is the wrong computer niche. The Natami was gaining interest by developers and ex-Amiga programmers as can be seen in Natami forum posts (developers were asking instead of being asked). It was generating Amiga excitement not seen since the collapse of C=.
Why not follow Apple's lead and forego custom designed chips and buy 'off the rack'?
Apple would be the world's 3rd largest MPU manufacturer in the world (behind Intel and Qualcomm but ahead of AMD and Freescale) although the statistics often combine Apple with Samsung who provides the foundry services. These are Apple custom designed SoC processors by the way.