My feeling is that regulators will insist that investors are accounted for and the blockchain will verify if they can back the investments. So long as they buy a coin when someone wants one on the ETF then all is fine. The liquidity of it all will tone down the greed factor as much as Wall St. ever could. It will allow an avenue for the new investor to Bitcoin and need not be seen as a negative thing. The motivations of gaining SEC approval might be more of a Hail Mary Pass with that 30+ Trillion Dollar Debt to themselves more than anything else.
My feeling is that there are many on the race to power in the USA which can see the US gain some of its financial clout by going the route of El Salvador by making Bitcoin legal tender.