The game changer could be the fact that many more merchants start accepting Bitcoin. Bitcoin was designed for the value to go up and early adopters to profit. This is because currency isn't going to be used by anyone if other people don't use it as well, so it gives people incentive to start using it. When many people start using it and the price stabilizes, there is no reason not to use it anymore. It will be well known and accepted by this point and there will be no benefit in hoarding it. This doesn't mean everyone will sell once the maximum value is reached, since now they don't need to sell it, it is currency like any other, why would you sell currency for currency. Bitcoin would still be more useful then fiat, so everyone can keep it. This is why people say you should never sell, because by the time it reaches it potential, you will not need to sell it to use your profit.
Never is a long time, eventually price should stabilize, that is the point. Amount of Bitcoin users is growing all the time and so is the adoption of Bitcoin by merchants. This would mean that the price won't be dependent on speculation and emotions anymore, so it should stabilize. Once you start accepting Bitcoin, it is unlikely you will stop, why would you? This means that users don't need to worry about the price going down, since adoption won't and that is the only thing that gives it value as a currency. It is designed for people to benefit form other people adopting it, this is what drives the adoption in the first place, which is necessary for currency.
It should. It is what gives you incentive to help setup the system. In order for currency to work, you need people to have your currency and know how to use it. Then it is just up to the agreement of using it as something of value, which is the merchant adoption we were talking about for which are obviously incentives.
It is not really a conflict of interests. You want it to stabilize, because it can't go up forever so there will be a maximum of your earnings and this will be when it stabilizes. You can't expect that something will keep going up forever, there is a limit to how many things of value are there in the world. This is your end goal, buy until it is so largely adopted that it is stable and you maxed out your profits, at which point you stop buying, but still have no reason to sell as people accept it as payment and it is better then currency you would sell it for.
You can and should do both. When you want to buy something and you can buy it with bitcoins, then do so, it is easier, more secure and private that way and you will be driving up the value of Bitcoin by increasing it's adoption. If you want to sell something, accept selling it for bitcoins for the same reasons. If you don't need to buy anything and don't want to sell anything, then don't and keep at least a portion of your savings in bitcoins, that way you profit and increase the adoption, since merchants will have more people ready to buy their product with bitcoins.