I see no reason why it wouldn't be, but it's a niche within a niche, and support probably won't be so widespread. Additionally, you'll probably need to compile pretty much all your software yourself. If you use a Portage-like system, that won't be too much of an issue providing the repositories are kept well updated. It's definitely doable...just not an ideal situation. I'd personally rather just use OS X.
And you're relying on rumour articles to make the statement that it's 'inevitable'? I expect a fair amount of waiting due to all the thermal issues related to the G5.