Whilst it's true that holding on to bitcoins will reduce supply to the market driving up prices, if everyone holds on the can be no wide scale adoption of the currency and so it can never take off and no money can be made off your potential investment
I promise, if every other bitcoiner holds onto their coins until the spot price is $1,000,000 per coin, I'll spend mine. So don't you worry about it. Keep hodling until then.