I don't know if Adell is the next Lewis Brinson or the next Albert Belle, but he is definitely a top prospect. Even the best prospects have a very low chance of reaching their ceiling. He is just one of those guys with a ton of tools but a wide range of potential outcomes, due to some significant weaknesses in his game.. which is to be expected for 21 year olds.
From a hobby perspective, yeah... we are looking at a ton of risk. Obviously the market cap on a guy like Adell is very high and there are much safer options. That said, there is plenty of money in other guys that are unlikely to pan out but also don't have half of the raw potential that Adell has.
Full disclosure: I have a pair of high end Adell cards and still not certain what my plan is at this time..