Wow thank you for all of the advice so far, I welcome it.

Having posted in the alt-coin forum here (I'm still pretty convinced that ETH at least will be around for a long time and is very safe for a cryptocurrency), I am getting mixed signals.
The alt-coin forum seems to think that bitcoin will not be the only winner, even long-term. There does not have to be one currency to rule them all, just like in the real fiat world.  Yes, the dollar is pretty dominant, but there are many others.

I wonder if this striking difference of opinion reflects personal experience or personalities (risk adverse people flock to the bitcoin forums, risk-tolerant types hang in the alt-coin forums)