If you look at normal currency vs. Bitcoin I'm assuming bitcoins will be constantly on a 2-3% rise because of inflation on any other currency. So it depends what you're comparing it to. If we're talking about a currency with normal inflation then yes it'll be relatively stable at some point but if we're talking about currencies that are new or currencies that have a higher rate of inflation (3rd world countries) bitcoins will seem less stable there even if it's stable in terms of the value in another country. Either way you'll be better of with bitcoins rather than fiat!
By looking at one side you can tell that bitcoin is better than fiat, but when it comes to being use for daily transactions fiat is not question the best. The reason why we are using fiat as we can easily use it even in the physical world and everybody recognize it as a legal tender, while bitcoin is not that popular.