What is your exit strategy?
I will sell bitcoin when it reaches the highest price and I believe it will go to that price.
Did most of you buy through coinbase and will just transfer back into there?
No, I don't buy through Coinbase. Fortunately, I have a friend who always helps me to buy bitcoin and then I can send it to the exchange so I can trade for any pairing.
Would they be able to support millions of people withdrawing hundreds of thousands of dollars?
Coinbase will be able to support people for withdrawing? Hm, I think they can but the problem, how good their server to anticipate the increasing of the traffic on their website? Because if millions of people withdrawing all of their money, then the traffic will increase higher and they need a strong server to handle that.
Crypto seems fairly liquid but again if it shoots to the moon, how liquid will it really be?
I don't get it your question, so I don't answer it
We could use the other exchange rather than use Coinbase only, and I am sure that we can found a reputable exchange with easy. I have local exchange and sellers that could help me to withdraw bitcoin.