Forget about Lambo and mansions as 7-10 years from now you 1BTC isn't enough to have one of them unless you sold your BTC or unless if 1BTC is worth $500k. Well, that sounds impossible, right? I'll just be predicting it reach $200k if the demand will tend to improve as well as the adoption but if not, we can still see it below $100k.
To imagine that 7-10 years from now Bitcoin has become a legal tender is gonna be possible but not all countries will adopt it. So, if you are in a country that accepts Bitcoin, then you're too lucky.
Besides even if in the future we could convert one BTC in a lambo should this be done? After all even luxury cars lose some of their value after they have been used while bitcoin goes up in value the longer you hold it, so it seems like a bad business decision to get rid of something like bitcoin for something that is just a frivolous purchase, now if you have a lot of money then you could afford it without spending all your bitcoin, but still I think there are other ways to spend our money and get more enjoyment out of it.