@Karlos,
As you well know, there are fanboys in the extreme for just about everything on the face of the planet, both Amiga Next Gen systems have more than their share of them that make stupid comments all the time.
As for why the G5 now, I would counter that support for the G5 is not coming now, nor is it going to be any time soon that it is released, as the MorphOS Dev Team does have higher priorities to work on. I think part of the confusion is that many MorphOS users spread their wishful thinking as rumor like they are facts and the Dev Team is fairly silent about what they are working on at any given moment. Also, from what I have observed and guessed, I believe that the MorphOS Dev Team is a much more loosely organized group of enthusiast developers that are basically free to work on which ever parts of the OS to see if it will work, explore new possible targets to port MorphOS to in the future, etc. There is obviously some coordination and discussion about priorities and desired completion dates for certain items or targeted models that the Team as a whole wish to support and which models or platforms would be good candidates to support next, but only a member of the Team could know exactly how they are organized and how the workload is assigned, or otherwise divided between them. With very little information officially released by the Team regarding what they are working on, or even which models of the PPC Macs they intend to support, there is a ton of speculation and rumor everywhere.
I haven't checked the official website lately, but the last time I was there, no mention of official support being planned for even the G4 PowerBooks was listed, not to mention the G5 PowerMacs, even though videos and at least two public demonstrations of the G4 PowerBook running a beta version of MorphOS have been presented, by Piru I think. I am very sure that support for the G4 PowerBooks will eventually be released, but unless the support for the G5 PowerMacs is much easier than myself and most other people assume, it will likely be a long way off before such support is released, or even announced officially.
As to your other question about what do we need the G5 power for, and there are no Amiga apps that need that kind of power, you are obviously right for 99% of the apps, but with the old 68k apps needing to be run through a JIT engine and not natively, any demanding Classic Amiga app, such as 3D rendering, will benefit from the extra power. But more important in my minds eye is that the extra computing power will open a few programming opportunities that everyone thought could not be accomplished on any Amiga computer in the past. With G5, or PA6T power and if/when better graphics cards are supported, it will be possible to create better Amiga applications in the future than might be possible with only the current power of a 1.5GHz G4 MacMini, or in AmigaOS4.x's case, a 1GHz G4 Pegasos2, or AmigaOne.
Concerning your argument that we all have other computers that can run anything that can be run on a G5 or PA6T Amiga system faster and cheaper, not everyone wants to have to switch back and forth between different systems and many of us hope that with a sufficiently powerful Amiga system, more Amiga programmers will return to coding new programs for us to use and we might be able to do 100% of what we now do on multiple computers on just one powerful Amiga computer. Not everyone here HAS to have all the latest software, or web plug-ins to satisfy our computing needs and I would say that many of us here at A.org are the die-hard few remaining Amiga enthusiasts that would prefer to ONLY use an Amiga computer and OS and not have to boot into any other OS ever again. Maybe that is not realistic, and some will say it is not possible, but everyone has different computing styles and needs, so I say to those nay sayers, don't tell me what I have to own, or have to run to be happy with my computing experience.