LeBron James is 23 years old. When his contract runs out he will be 24. If at that time he goes overseas for two years to the tune of $100 million plus endorsement money, when he returns to play in the NBA he will be 26 and have the ability to sign with anyone. If he wanted he could sign with the defending champ for the MLE because with all the cash he made in Europe, he wouldn't necessarily need to sign for a max contract that would probably only be available from a really bad team.
Michael Jordan, His Airness, who Kobe and LeBron will always compare their legacy to, was 28 years old when he won his first title. He then won 6 in the next 8 years. With a 2 year head start, a boatload of cash already in his pocket, and the ability to hand pick his desired destination, LeBron could still go on to win more titles than Jordan did.
So I think the point I am trying to make is don't discount LeBron's legacy because he went Euro and for the Euro for two years. He is still remarkably young for someone so accomplished and going to Europe and pocketing all that money could very well be just the thing that will free him up to make the decision to take less money to go to a contender or champion than to go to Brooklyn and be stuck in the same rut that he is stuck in in Cleveland.
So before dismissing LeBron off as a money grubbing afterthought because at an extremely young age he decided to make tons of cash and give him the luxury of hand picking his future, think again. It could very well assure his legacy.