Bitcoin is commonly compared to Gold and I agree with BTC proponents who state that most of Gold's value is driven by speculative investment, however in the long term (over centuries and even millenia) it has a demonstrated real return of zero. So Gold has preserved wealth.

Bitcoin might do the same, but for this to occur it will always need new liquidity as it lacks intrinsic value. But this also implies that the real return will be zero over the long term, like with Gold. Moreover, as it's value comes entirely from its price, the door to the 'price value' of Bitcoin (or any other similar asset) reaching the Moon or zero will always be open.

However, Gold does have intrinsic value (10% annual use in industry) and has, over millenia and at present, an aesthetic value (40% in Jewellery). Which would probably classed under Sign Value in semiotics. So it has intrinsic, exchange, symbolic and sign values too.

Note that over the long term, most commodity real returns have been zero or even negative. Unsurprising, as we have gotten far more efficient at extracting them.