Probably quite a while, as NVIDIA currently doesn't mention cryptocurrency mining publicly to keep investors from worrying about the sustainability of their recent revenue growth.
I don't know about the deep learning side of things, but on the mining side of things, over the past month, my calculations are that ~50,000 GPUs are added to mine the major GPU-minable coins every day -- from roughly one million GPUs on April 1 to about 3.5 million GPUs now. At an average of $250 revenue per card, that'd work out to ~$13M revenue per day in GPU sales for cryptomining, split between AMD cards and NVidia cards. This, however, is up about ten-fold from March, and in all likelihood will return to those levels as mining returns inevitably decline.
Source of this data is my own calculations using historical data on mining difficulty for the various coins, plus benchmarks for typical/optimal-ish GPUs used to mine each coin.
Yes, I am assuming that all mining is done with GPUs for ETH/ETC/ZEC/XMR and some others. I'm only including coins which are currently profitable to mine on GPUs, which I take as an indication that those algorithms have seen little/no efficient ASIC implementation yet. I'm thus not including bitcoin, since GPUs are little more than space heaters mining bitcoin; and I'm not including e.g. lbry and litecoin and some others because I don't know enough about the ASICification of those.
It's possible, though, as you suggest, that there are some folks running ASICs or improved hashing algorithms at a small scale, small enough not to overwhelm profitability of GPU mining but large enough to muddy calculations which assume that all mining is being done on GPUs.
Hard to say... most recent quarter had datacenter at $409mm in revenue. Mining falls under gaming, which has grown ~$600mm since 2015 to >$1b per quarter today. Try to buy a gaming GPU today and you won't be able to -- they're all sold out because of cryptomining.
Nvidia 1050 ti is almost untouched for mining purposes and there is 10% price increase in 1060s and 1070s. 1080s & 1080 ti you can get for retail. The GPUs the are in insane demand are AMD RX 580/570/480.