"The adoption of bitcoin (BTC-USD) by institutional investors has only begun, while for gold (XAUUSD:CUR) its adoption by institutional investors is very advanced," says the quant team at JPMorgan.They note the Grayscale Bitcoin Trust (GBTC) has inflows of nearly $2B since October vs. outflows of $7B for gold-backed ETFs such as the [[GLD]] and [[IAU]].More: According to the note, Bitcoin accounts for just 0.18% of family office assets vs. 3.3% for gold ETFs - a rebalance could bring many billions to the crypto at the expense of the yellow metal. They suggest a possible pair trade, buying one unit of GBTC vs. selling three units of GLD.At the moment say the quants, Bitcoin's big recent rise has things pretty perky, and a pullback may in order. In the medium- to long-term, however, gold faces a "structural flow headwind."Speaking of more mainstream acceptance, none other than Fidelity is partnering with BlockFi