>they're not in immediate danger of being replaced by another aggregate news and/or niche site //
I'd say they're not in immediate danger because they're not making a profit and most businesses that have the sort of money needed to support such an effort (ie the large traffic) don't want to waste money on something that's not going to make a profit. Indeed Conde Nast appear to have only recently and quite reluctantly allowed reddit some more resources.
Explosive growth in traffic, yes, what's the balance sheet look like.
I've never really looked at Reddit as a company that wanted to grow under Conde Naste. They were able to demonstrate their value through influence. Now that they are a separated from Conde and under new expectations one level above from Advance, we can see what it is they're made of and if they're really going to be able to be profitable.