Is it a comeback or a swansong? Will he sing or lipsynch? Has he still got the moves? Michael Jacksons brief appearance on Thursday at Londons O2 Arena,where he plans a series of 10 concerts starting July 8,raised more questions than it provided answers. The 50-year-old did at least show up,looking more robust than in recent photographs. But his announcement was confusing,and left reporters and hundreds of screaming supporters wondering whether his first series of gigs in 12 years would actually be his last. These will be my final shows. performances in London, Jackson said. When I say this is it,I mean this is it. Ill be performing the songs my fans want to hear. This is it,this is really it,this is the final curtain call. Randy Phillips,president of AEG Live,which signed Jackson for the concerts,had few concrete answers. He did not rule out more concerts in London and elsewhere in the future,and much more than just music appears to be riding on the summer shows. None of us are sure, he said. I didnt want to get so far ahead of what he wanted to do. Were holding dates, he added,referring to the O2 Arena where Prince performed 21 nights in 2007 to critical acclaim. We dont know how big the demand will be. On Jacksons health,Phillips was more confident,saying the performer,who has looked frail and gaunt in recent months,had passed a lengthy physical examination. And asked if Jackson would sing or lipsynch on his eagerly awaited return,he replied: Hes singing. AEG Live have a plan to work with Jackson for the next three-and-a-half years that involves concerts,new music and movies,including a big-screen adaptation of Jacksons seminal hit and video Thriller. The agreement could earn Jackson well over $400 million,Phillips said,although that would depend on all of the ventures discussed being carried out. While the man who made 1982s Thriller,the biggest-selling album ever,still has what it takes to move his fans to tears,many commentators were less impressed.