I would not invest in ETH. When the change to PoS is coming, all miners would change to an other coin. It would make no sense for the guys with the big hardware centers to shutdown their hardware and forget investments. So no one would mine ETH and the time for approved transactions would rise from seconds to hours! This would kill ETH. Without the possibility to mine a coin, there is only a chance to wait for an artificial pump, otherwise the coin would catch dust.