Personally, I think GPU miners will be a bit disappointed moving into ASIC mining, but if you pick the right entry and exit points, it can be massively profitable.
Absolutely, I know that I'll have to pay more attention to the depreciation of the equipment and the revenue:electric ratio. An older miner with $3 revenue/$2 power is much more risky than a newer model with $6 revenue/$2 power. The more bullish I am on BTC price, the more the balance shifts toward older equipment.
I'll but ASICs on at least 3 algos in order to manage the risks of just 1 coin going down. If DOGE crashes, my Antminer L3's are worthless. If Zcash crashes, my A9 ZMasters are useless.
But a lot of GPU miners will be disappointed and wish they did ASIC mining instead if ETH PoS indeed comes this summer...