It seems to me that you have not noticed how the entire cryptocurrency market is regulated. This is the real regulation. Maybe for this reason bitcoin is losing its popularity?
Probably not. IMO bitcoin is not losing popularity at all. It's just that those who have bought at all time high bought bitcoin merely out of pure greed and are selling their bitcoins on low prices now because they easily believed analysts and have been driven by FUD and FOMO.
Another parabolic increase after a few months of accumulation and blow-off? Improbable, no matter how good the ETF is, but possible to make the similar climbs back to $15-$20k.
I do think that it is possible because of possible unforeseen good news in the next coming months but the chance of it happening is below 1% and if it did reach $50,000 by the end of 2018, I expect a massive sell-off afterward.