Sure, if they can find a way around dealing with HBM2 and higher TDP. Anything's possible, but it doesn't make much sense speculating around this. Besides only the bigger miners stand to make a profit or break even until the next big hype around another coin. So not for at least 6 months to a year (if all mining cards and RX xxx are sold out).
I've seen a good number of crazy folks in desperation to get even a single coin off mining. My predicted forecast is that them miners will hijack the new GPU's for hope that they mine better. Ofc to the desperate, the TDP alone would not set them back, probably the number of PCI-E slots they have access to...
Nope. I've tested Frontier Edition vega and if that is anything to go by, the combo of both HBM (which hampers mining performance significantly) and power use will make it basically DOA for miners. That isnt to say some miners wont buy the cards, but most likely not like polaris was. Because Polaris has the mix of specs miners want- low power use, good performance (and GDDR5 so there isnt a memory performance issue).
So it's more than likely that vega cards are not going to be bought up like polaris ones.
Side note: Mining on GPUs is dying anyway so theres also that.
Although, recent reports indicate the newer drivers dropping with the RX Vega release make it ridiculously good at mining. To the point where it may still exceed other cards in hashes per watt of heat.
A whopping 100mh/s will only bring in about $17/day next week. In 3 weeks it'll go down even more. Unless you have 10 - 20 multi-GPU systems (6 - 10), they'll make some money for a few months.
There are companies running dozens of systems comprising hundreds of cards 24/7 with enough money to charter 747s to bring in shipments of graphics cards to them, which each card running 30-50MH/s. You can imagine what would happen if they suddenly jumped up near 100 MH/s per card.
You're right, a lot these companies usually get theirs through other channels, not usually through retail outlets. Either way, if it's over 50Mh/s it would be worth it for them since you're downclocking and undervolting anyway in mass environments.