There are different risks for the different classes of sports cards (pre-WWII vintage, post WWII vintage, junk wax, modern, ultra-modern) and a couple that apply universally.

Rising population reports

First, with the recent explosion in interest in cards as investments came an explosion in submissions to grading companies, causing PSA and BGS to both pause their services, which caused a ripple effect throughout the industry. Now, with both companies working through their backlog, the population reports have been changing immensely, with a lot of cards becoming more common than previously expected. This shouldn’t affect numbered parallels or vintage cards as much, but for modern cards, we are already seeing some ridiculous numbers – there are now over 20,000 PSA 10s of the 2019 Zion Williamson Panini Prizm and nearly as many PSA 9s, for example.

Active player risk

For any cards of athletes still playing, there is always the attendant performance and injury risk. For younger players (think Luka Doncic or Joe Burrow), this is a bigger risk than for established greats (LeBron James or Tom Brady) who have a much higher floor because of their existing accomplishments. If a young athlete with high potential does not pan out, the value of their cards will plummet. If they or their team have a poor season, the prices will drop in the short-term. For modern players, so much of the value is tied to how fans are currently feeling about them and that is almost entirely tied to whether they are doing well and whether their team is winning.

Cultural relevance changes

For vintage cards, except for the absolute legends of a given sport, there is the risk that the player will lose cultural relevance going forward. This is not a risk for Michael Jordan cards, but it may be a risk for Wilt Chamberlain cards. It is certainly a risk for Nikola Jokic cards. The icons for older generations may not hold their value as well as those who remain icons for younger generations. The same can be said for overall sports - the ones more popular amongst younger generations are going to hold their value and provide less risk than those who have seen their popularity decrease. Modern baseball cards have generally struggled as the sport has seen a decline in interest from Gen Z, whereas soccer cards have been on the rise as the global collecting market grows.

Declining scarcity

Finally, every time sports cards have seen increases in popularity, card companies have responded by overproducing items and flooding the market with supply, causing prices to go down. We may be in the beginnings of a new junk wax era and it’s only likely to get worse going forward. There are now so many parallel and insert cards that even the “top” cards have become less scarce. Also consider that nearly all collectors know now to preserve the cards so the vast majority of cards get high grades which dilutes the value of highly graded cards. With these factors, it is easy to envision a future where even PSA 10 rookie cards of top players produced now will be so common that they barely have any value.