By Kieran King Cristiano Ronaldo has joked he will keep on playing for ’10 more years’ after the Portuguese superstar dropped a major hint on his retirement plans. The 38-year-old has been in sensational form for Al-Nassr this season, scoring 30 goals in 31 matches in all competitions. He is currently the top scorer in the Saudi Pro League (20), with Aleksandar Mitrovic (17) and Georges Kevin N’Koudou (14) in second and third respectively. Ronaldo hasn’t shown any signs of slowing downsince his move to Saudi Arabia 12 months ago, but the five-time Ballon d’Or winner, who turns 39 next month, w…