Update plugin settings option_name for big plugin update

I think changing array keys is more of a PHP problem

// Get entire array
$plugin_options = get_option( 'plugin_options' );

$new_options = array();

if( isset( $plugin_options['ga_accountId'] ) )
    $new_options['ga_account_id'] = $plugin_options['ga_accountId'];

// Update entire array
update_option( 'plugin_settings_general', $new_options );
// Delte old array
delete_option( 'plugin_options' );

Any end-user who might be using using your plugin’s options for something in their theme, will get errors. But if you are going to rename things, plugin_settings_general should be name-spaced with your plugin’s actual name.