If you're looking for a card to have high value in the future you want an all around high impact player. Look at cards that are high priced, guys either were leaders in HR's or were some of the greatest players of all time. Now, that being said, there are no catchers out there with as high of a value as a trout or Harper right now. Even one of the greatest catchers of my time, Mike Piazza, mint rookie card is worth about $90-$100. Bryce Harper and Mike Trout have spent, not even a full season in the league, look at harpers team USA 2009 card. Look at Trouts rookie autos. Not even a full season! Buster Posey's rookie card doesn't even come close. Strasburgs are low in value too. Mostly because there's no phenom pitchers that impact the game like hitters do. They have to prove themselves more with Cy Youngs, MVPs and rings.
Regardless of everything I've said, the proof is in the pudding and this hobby is a lot like baseball tickets. Meaning, no matter what their card is now, if they don't produce, the value goes down. Also, the value is driven by hype just like a baseball ticket. If your team sucks, tickets are cheap. If your team rocks, tickets are expensive. Just my thoughts.
Regardless of everything I've said, the proof is in the pudding and this hobby is a lot like baseball tickets. Meaning, no matter what their card is now, if they don't produce, the value goes down. Also, the value is driven by hype just like a baseball ticket. If your team sucks, tickets are cheap. If your team rocks, tickets are expensive. Just my thoughts.