You have nothing to gain by making these predictions, just like how everyone who predicted the fall of the Internet are now laughed upon. Furthermore, even if Bitcoin DOES go down, it's not like you'll be applauded for being an 'oracle' just because you predicted this either. Pretty much everyone who's risk-averse or doesn't understand the technology is saying the same thing.
Why not actually learn how the technology works, so that you don't make these shallow snarky remarks that sound exactly the same as the conversation I had with my uber driver last night, and instead maybe yourself could come up with a solution?
Regarding all the reasons you pointed out, except for the transaction fee issue, the rest are really non-problems. Just because fewer people buy mining devices you think it will go down to $300? Just because you lost your Bitcoin because of your carelessness, you think Bitcoin will go down to $300?
Transaction fees are really the biggest issue right now, and there are tons of different approaches people are working on. Just like the Internet had hard time scaling in the early days I'm sure people will figure it out.
One thing I find annoying about mainstream media saying Bitcoin will die is how they think Bitcoin is some fixed thing that's doomed because it won't evolve at all. I expected better from HN audience. Bitcoin is designed to evolve through forks and that's the whole point. People will find various ways to fix all kinds of challenges because financial incentivization is built into the protocol.