They didn't literally mean that unless you see somebody bending down, feeling the wrist and saying, "they're gone", that somebody isn't dead! :lol:
If they were going to bring him back, they would have at least mentioned his name in the last 2.5 seasons.
He was part of Sydney's 'normal' world, and him dying was the thing that pushed her into this new world (the CIA, Vaughn, the Prophecy etc.) - ie he was the catalyst.
Catalysts don't reappear after two and a half years. Apart from anything else, 90% of the viewers wouldn't even know who he was. I'm sure you will find most people haven't watched every episode of Alias, and many would have become fans after the pilot. Others wouldn't even remember him, even if they had seen the pilot.
The day they bring Danny back from the dead is the day Alias is axed. There is no point to him coming back, and apart from anything else, it's just stupid - even for Alias.