With Bitcoin, the "penny people" already had a couple of chances to cash out, broadly speaking. Maybe someone will estimate, by studying the BTC transactions, how many ETH people would cash out at various price levels, given the past behavior of BTC, given an equal increase in value. So maybe 30% of early adopters sell off after a 10000x increase, and then you could try to predict when people will start to dump ETH, ceteris paribus.
The way BTC was distributed initially was very different than how ETH was distributed. No BTC was ever given out that wasn't earned through mining. ETH on the other hand sold a large amount of ETH in a pre-sale. Literally all people did to get it was give money to the project's developers and they were allocated some ETH.
If you are mining you have probably invested a lot in equipment, time, and other costs to get the coins you get. With ETH there was literally no investment of anything except money.
