They're going to more heavily regulate it over time. That's how they're going to deal with Bitcoin. The goal will be to keep it at the margin (compared to other assets, other investments), along with gold ownership. They can and will easily accomplish that outcome (which also doesn't prevent Bitcoin from gradually becoming a multi trillion dollar entity given the scale of the global economy).

There's likely to be no need for the US Government to worry about, for example, confiscating Bitcoin as FDR's administration did with gold. Today Bitcoin is comparable to Facebook's market cap. Back in FDR's day the scale of US gold holdings in relation to the US economy and its asset base was radically greater than these entities are today (today gold holdings in the US are trivial compared to the US stock market or housing market). For that type of confiscation event to happen Bitcoin would have to become a super giant asset vs global currencies, which will only occur if the US Dollar, Euro and Yen collapse or something close to it. If that happens, all manner of confiscations will be on the table, a lot of very, very bad things will be occurring.