mypmpro-add-renewal-date-email-var.php

<?php //do not copy

/**
 * This recipe adds a !!next_payment_date!! variable to your email templates.
 * Note that this will only work with recurring levels and not for levels that expire or are once off.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */


function mypmpro_next_payment_date_email_var( $email_data,$email ){

    if( ! function_exists( 'pmpro_next_payment' ) ) {
        return $email_data;
    }
	
    $user = get_user_by( 'email', $email_data['user_email'] );

    if( ! $user ) {
        return $email_data;
    }
    
    //Get next payment date
    $next_payment_date = pmpro_next_payment( $user->ID );
    
    if( ! $next_payment_date ) {
        return $email_data;
    }
          
    $email_data['next_payment_date'] = date( get_option( 'date_format' ), $next_payment_date );

	return $email_data;
}
add_filter( 'pmpro_email_data', 'mypmpro_next_payment_date_email_var', 10, 2 );

The snippet returns the date of the current payment in the Recurring Payment Receipt email. Reason, the subscription details are updated after that email has been sent out.

Here's a variation that gives the expected next payment date in that template, calculates date from the level & order details: https://gist.github.com/dwanjuki/d9a1fb83101af2f91e7ec3d9e59a899e