While I agree with your precise thoughts on the consequences for exchanges — I am not sure about your views on currencies and ICOs.
If coins/cryptos are not a security or at least real currency — how can one buy a security with these? It does not really make sense from the SEC to make the one (token in ICO) a security, but call the other (coins) neither a security nor a currency…
Also — if this ever changes — what would it mean? Would coin projects in the US be as much in danger as the exchanges might be, now? Would it be enough for the exchanges to comply with KYC (Know your Customer) rules like Kraken & Coinbase do or would they really need to get registered?
But actually I would very much welcome the decentralization of exchanges — that would be an awesome result of the SECs move. Of course, today some already exist, but they have not solved the downside in a decentralized exchange for trading — liquidity and the time it takes to get orders through — but I believe the next generation is close to be launched (e.g. Raidex from Brainbot).
Regarding ICOs — I think one should keep in mind, that at least some of the Ethereum based ICOs (using the ERC20 standard for creation of own tokens on Ethereum) showed small numbers of investors — the BAT had only 150 addresses gathering what then was worth 35 million USD. Today they openly thank VCs on their site (https://basicattentiontoken.org/).
And TenX which had quite a crowd of addresses reported openly, that about 1% of all investors invested 60% of the ICO…and that is without the presale they did. And then there was the same craze with Bancor.
So — maybe we need to look a bit differently on ICOs.
While the process and technology offer a true decentralized funding mechanism — we are not & have not been there, yet!
At least the ERC20 ICOs seem to show, this great invention is being used mainly by institutional investors like VCs to get into the markets — and probably by all the rich ICOs of 2016 and before, who need to diversify their holdings….as a 4–5 million USD ICO of 2016 now probably has 50–200 million USD worth of ETH…
So — to make a long story short — regarding ICOs, lets keep in mind, it probably is not a crowd instrument — yet. 😉
One more thing: Since May most ICOs blocked US participation through IP addresses anyway…so its not really so new…