He also seems to think many or most altcoins might possibly decline to near 0 in 2019.
I dare anyone believing altcoins to become near worthless to short them, because instead of altcoins going to zero, your balance will go to zero.
We are dealing with people not caring about fundamentals, decentralization, currency aspect, etc. It all contributes to a situation where even the worst altcoins are worth billions which is pathetic but the damage is done already. It's impossible to bet against altcoins long term speaking because you are really going to burn yourself. Altcoin's get fueled by Bitcoin's increases and as long as Bitcoin keeps increasing, which it keeps doing, altcoins will follow.
Inclined to agree, but only when dealing with the top-tier or even second-tier alts. I don't have a specific categorisation that would qualify alts to these tiers, but having their own blockchain and active development would have to be a must.
I do believe that the hundreds of tokens that have launched in the past year are already struggling and the bulk of them don't have strong communities backing them, nor developers keen to spend even more time to revive their value and this will just further translate to delistings, and 0 liquidity, essentially, worthless.
But like you, I truly believe crypto is Bitcoin and Bitcoin is crypto. The fortunes of the entire market rest solely on Bitcoin's performance. For now, and for the foreseaable future.