I don't think you need to buy them (unless you want to gamble on their value going up) - just be willing to accept them as payment in the future. As more people see they can easily spend bitcoin, they become more willing to accept it as payment, and the userbase grows (bringing more price stability, hopefully)
I don't think userbase has much of a correlation to price stability. Even commodities like gold or oil have exhibited periods of high volatility even with a large "userbase"
Also, while we're talking about price, people sometimes conflate bitcoin transaction volume with bitcoin price, forgetting that for every buyer there is a seller. As a means of transacting, bitcoin is great, especially for small amount or across borders. It makes no difference what the price of bitcoin is as long as the buyer and seller are immediately converting out of bitcoin and into their local currencies - and that has no long term impact on price.
Unless of course many people notice rising transaction volume, confuse the trend, and then invest in bitcoin, which then becomes a self-fulfilling prophecy.
"bitcoin transaction volume" is worthless. Anyone could easily make a new record in btc txs for a thousand dollars. If I send money to myself, it counts as a tx.
The real concern with bitcoin is that it can only support 3 transactions a second with the current codebase. Gavin wants to fork it to get rid of the block size limit, but there's been opposition.
