First off, Cash is trash. Let's not confuse purchasing power vs. true capital appreciation via investment. Your purchasing power is going to evaporate if you hold US dollars or companies with low growth primarily exposed to the US. US stocks might go up, but most won't really increase your purchasing power in my opinion over the next 10 years.
The number of bonds with real negative yields is gigantic now, so you can't go there for investment or preservation. Growth will be the name of the game to outpace inflation, and not much in the US fits that mold. FANG stocks are bid up so big precisely because there isn't any other place to hide domestically. There will be tremendous growth in emerging markets, but fund selection will be important. Most of the emerging market funds are market weighted and therefore overly exposed to a few countries. I'd avoid those funds and try to pick a few individual country focused funds. For some that might include China, but that's a bit of a black box and geopolitical risk is high. I like things like India and Brazil and I'm avoiding Japan and most of Europe.
With US debt monetization rapidly ongoing, and the Federal Reserve purchasing something like 60% of treasuries since the crisis, precious metals should hedge that risk and preserve purchasing power. Gold confiscation or more likely just taxing the holding of precious metals is a risk though. Some commodities should do well, but many are hard to own directly and trading futures isn't for most. I'm not as bullish on oil, gas, and coal. The move to renewable energy is real and rapidly increasing worldwide. I would be cautious of owning natural resource extraction companies that operate in localities that have a tendency to nationalize these assets. Copper should do well, but again pick your miners wisely as many operate in localities that will nationalize resources given enough national debt pressures.
I don't like rental real estate in the US currently, but that may change in a few years after weaker hands need to unload rentals. If i had to pick a market it would be in the Midwest. Traditionally, median home prices have tracked inflation for 100 years. We had the housing bubble that really was the first time things got really above rate of inflation and that didn't go well. We briefly got back to the trend line around 2012, but things inflated back up again, probably because of artificially low interest rates as set by the Fed. You can still find deals occasionally, but I'm having a hard time finding much. Look for houses you can easily add an extra bedroom and maybe an extra bathroom and you really can't do that unless you're willing to do the hard work and walk properties, and get a team in place to rehab properties. Then you have to be willing do endure all the things about being a landlord that suck.
Lastly, monetary history isn't really talked about or really taught much, but world reserve currencies never last forever and for that matter no fiat currency has either. Our dollar is back by the full faith and Credit of the US government. Who is willing to lend Uncle Sam $1000 right now for 10 years at 0.60% interest? I'm not. There is a non-zero risk that we will have a currency collapse and for that reason I do think people should have some precious metals and other asset classes besides domestic dollars and companies. Some argue bitcoin too, but that's a whole other debate. I think bitcoin is likely to fill the role gold once did and get confiscated/made illegal. I do think physical cash will largely if not outright disappear over the next 20 years, if not sooner. Many countries have already removed large denominations from circulation. The largest bill in China is worth about $15. The Euro removed their 500 denominated note from circulation. Fully digital, government mandated, currencies are coming.
