While OS4 is the next generation of Workbench/Intuition, and is really great, unless changes occur on the hardware front there's not going to be enough money coming in to stop the whole thing folding. It's not something I want to happen, but I think it will.
x86 hardware isn't going to disappear for a while yet, and as AROS doesn't need to get a bunch of money to continue development, I don't think it will either. The more features that are added to it the more people will be interested, and provided at least some of these people contribute it will just keep gaining assets (be they advocates, developers, sponors or whatever), get more features, and attract more people in turn.
In short, IMO, AROS has the potential to end up successful, and quite possibly the largest OS of the Amiga community - this isn't Return of the Jedi, in real life everyone gives in to the dark side at some point ;-)
Oh yeah, and the mere fact this is being debated shows that it's considered a player in the Amiga hood. word. :-D
