Now that LeBron James has officially opted out of his player option for 2016-17, the focus turns to his next contract. It's been widely assumed by most that James will again sign another 1 year contract, with an option for the 2017-18 season. From there, he'll decline the option, and set himself up, along with many other elite players, for a huge payday when the 2017 salary cap rises yet again.
If He Stays With Cleveland
Because LeBron has been back with Cleveland for 2 years, he's considered to have "Early-Bird" rights. This means he must sign a minimum 2 year contract with the Cavaliers, containing no options in order to receive the full 175% raise he's inline for. This would mean a 2 year, $63.91M contract.
The alternative would be to request his Bird-rights be renounced, which would mean James would be eligible to sign a 1+1 contract (1 year deal + a player option), but at a maximum 120% of his previous year's salary. This would mean a 1 year $27,564,600, with a $29,631,945 player option for the 2017-18 season.
If He Signs Elsewhere
Assuming the team has an ample amount of cap space to do so (Lakers), LeBron can sign a contract of any length, with the maximum $30.8M salary for the 2016-17 - even a 1+1 deal.
In other words, LeBron would gain an additional $3M this year by going elsewhere.