If you mean bigger in terms of market cap, that would actually imply that more investment is needed, right? If you mean that the current approximately 6.5million units is not enough however, should point out that the currency is divisible to 10 decimal places, so this is mostly a red herring.

With regards to market cap, yes, that does need to grow in order that there be a stable value. This actually suggests that the price will pretty much have to go up though, as the expansion of the bitcoin supply is known and low while the expansion of the money cap through fiat currency buys is both unknown and unlimited.