If they seed it with BTC60k as they plan, that should provide plenty of liquidity as money makers just need to keep premium/discount to NAV to a minimum. Furthermore, with 0,15% fees they'll have the lowest fees from all ETFs (after teaser rates expire), so i'm actually expecting inflows to mini and outflows to the mothership.
This week should give us a glimpse of what it'll be like once GBTC runs out of BTC.
The funny thing is that we are now grateful to them because they launched this very competitive product for 10% of the funds instead of being so angry at them because they refused to lower the fees on the remaining 90% of their stash.