$50 is unlikely, but I think it's probably going to be $120, $120 is probably the final price of eth, $120 is probably a good purchase price.
you are forgetting the wave of panic that the drops cause. going from $350 to $250 creates a mass panic sell that now there is a huge number of transactions from people sending their coins to exchanges to sell.
Vitalik will capped Ethereum is 120m coin. I think Ethereum will fall to 150$ and sideway to bull run. You can set buy order in 50$, I set it is 150$ 
i have heard about the cap, also about sharding, also about switching to PoS, also about a 100 other things for the past 2 years and none of them have ever been started yet. so i wouldn't keep my hopes up.
besides 120 million is still HUGE!!! bitcoin is capped at 21 million.
if it gets to $50 i'll buy a bunch for sure.
no doubt about it.
you can see my old topic here too: https://bitcointalk.org/index.php?topic=1764234.0
bottom is where you should always buy at. not in the bubble. and one of the signs of the bottom is when nobody is talking about ETH anymore. when there is no more newbie accounts telling you how it goes to $2000+ that is when you know it is at the bottom.
