That is an assumption I'm not seeing.  Certainly there are many expecting a huge rally but on what basis do you believe people will be wanting to 'cash out'?  Some, certainly, but far from most I suspect.  And the reasoning behind my speculation is that anyone expecting another big rally is likely to believe bitcoin is not a flash in the pan and is therefore likely to be looking at it either as a long-term commodity investment as part of their portfolio or is holding onto it until such a time that more day-to-day transactions can be done in bitcoin.  In the meantime if things they want to buy start becoming available and good value in bitcoin the likelihood is people will buy more bitcoin to spend rather than bitning into their long-term stash.

My point is 'hoarding' bitcoin is better for bitcoin than hoarding pm, bonds, stock etc.   Spending bitcoin is better for bitcoin than spending fiat.  And should Bitcoin's long-term deflationary nature lead some to save a bit more and spend a bit less, whilst this may not be ideal to fledgling bitcoin-dependent businesses right now I'm tending to think it can't be a bad thing for the Bitcoin economy further down the road.