Sir Alex is coming up to his 26th anniversary of taking over the Premier League club and will be 71 in December, leading to suggestions that his time could soon be up.With United chiefs tasked with finding a replacement for their legendary manager, attention has already turned to former Barcelona boss Guardiola.A source close to the Spaniard told the Daily Telegraph that he is now actively seeking the right opportunity and his favoured option at this time is to manage in London.But with both the Arsenal and Chelsea jobs currently filled, United's chances of landing their number one target have been boosted.Sir Alex, United chief executive David Gill, a member of the Glazer family and Guardiola are believed to have met in New York during the summer.On the agenda is sure to have been Sir Alex's retirement plans and a possible move to Old Trafford for the in-demand ex-Spain international.A switch to Manchester City is another option for Guardiola, should Etihad Stadium chiefs decide to part company with current boss Roberto Mancini.