I don't have idea about that. does blockchain reside in all miners system or it is stored in a particular system? But well 700 GB is quit a large number. and database if only 3 columns of 700GB would be a huge database.
Miners find ways to avoid having to run full nodes with a full data set. Don't worry about the miners use of full nodes, worry about the miners being concentrated into small pockets of big industrial groups. All it takes is for two or three big miners to collude and they can fix the game to suit their ends. The only thing stopping them from colluding to rig the game is self-interest so as not to collapse the market price. If they get a government visit, however, governments don't care about corporate self-interests. Maybe we should have a mining Canary?
It is looking like users will just be users. So for the average person they can just use Bitcoin without worrying about such things as the backbone of the system.
We are likely to be in a transition state where home connections are going to reach max capacity. The transition then is going to be towards professionally hosted nodes.
This guy on r/btc posted some stats about his node consumption. He has 200mbit download and 20mbit upload, which is a very good connection in the western world:
------------------------+-------------+-------------+---------------
Feb '16 8.87 GiB | 22.38 GiB | 31.25 GiB | 104.62 kbit/s
Mar '16 109.58 GiB | 635.21 GiB | 744.79 GiB | 2.33 Mbit/s
Apr '16 144.85 GiB | 1.05 TiB | 1.19 TiB | 3.95 Mbit/s
May '16 112.24 GiB | 1.08 TiB | 1.19 TiB | 3.80 Mbit/s
Jun '16 95.28 GiB | 880.11 GiB | 975.38 GiB | 3.16 Mbit/s
Jul '16 90.72 GiB | 925.71 GiB | 0.99 TiB | 3.18 Mbit/s
Aug '16 178.99 GiB | 1.02 TiB | 1.20 TiB | 3.84 Mbit/s
Sep '16 133.12 GiB | 1.03 TiB | 1.16 TiB | 3.83 Mbit/s
Oct '16 115.43 GiB | 1.18 TiB | 1.30 TiB | 4.16 Mbit/s
Nov '16 15.69 GiB | 213.81 GiB | 229.50 GiB | 6.46 Mbit/s
------------------------+-------------+-------------+---------------
estimated 136.41 GiB | 1.82 TiB | 1.95 TiB |
He is reaching his connection limits, but that does depend on how he sets his in / out connections.
21 "subver": "/Satoshi:0.13.0/",
19 "subver": "/Satoshi:0.12.1/",
9 "subver": "/bitcoinj:0.13.4/Bitcoin Wallet:4.46/",
9 "subver": "/bitcoinj:0.13.2/MultiBitHD:0.1.4/",
9 "subver": "/bitcoinj:0.13.1/Bitsquare:0.3.3/",
9 "subver": "/bitcoinj:0.12.2/Bitcoin Wallet:2.9.3/",
9 "subver": "/BitCoinJ:0.11.2/MultiBit:0.5.18/",
7 "subver": "/Satoshi:0.12.0/",
7 "subver": "/Satoshi:0.11.2/",
6 "subver": "/Satoshi:0.11.0/",
6 "subver": "/BitcoinUnlimited:0.12.1(EB16; AD4)/",
4 "subver": "/Satoshi:0.9.99/",
4 "subver": "/Satoshi:0.8.1/",
3 "subver": "/iguana 0.00/",
3 "subver": "/bitcoinj:0.14-SNAPSHOT/",
3 "subver": "/bitcoinj:0.14.3/Bitcoin Wallet:5.03/",
3 "subver": "/bitcoinj:0.12.2/",
2 "subver": "/Satoshi:0.13.1/",
2 "subver": "/Satoshi:0.10.1/",
2 "subver": "/Classic:0.12.0/",
2 "subver": "/btcwire:0.4.1/btcd:0.12.0/",
2 "subver": "/bitcore:1.1.0/",
1 "subver": "/ViaBTC:bitpeer.0.2.0/",
1 "subver": "/Satoshi:0.9.1/",
1 "subver": "/Satoshi:0.12.1(bitcore)/",
1 "subver": "/Satoshi:0.11.1/",
1 "subver": "/Bitcoin XT:0.11.0/",
1 "subver": "/bitcoinj:0.14.3/Bitcoin Wallet:5.02/",
1 "subver": "/bitcoinj:0.14.3/",
1 "subver": "/BitCoinJ:0.11.3/",
1 "subver": "",
https://www.reddit.com/r/btc/comments/5b0g4x/remember_that_time/