The big question being asked by investors and millions of "macolytes" around the world is: can Apple continue its great run without Steve Jobs?

In the short term, the answer is undoubtedly yes. The senior executives at Apple are a close-knit bunch welded by their CEO into a team in his own image — design-driven, consumer-aware and very demanding of their staff. Apple has great momentum — the sales of Macintosh computers are at an all time high, the iPhone has changed the way we look at smartphones and iTunes rules the world of digital music.

There are several new products in the pipeline already — some of which might be coming out this summer — just in time for Steve to return in triumph perhaps. These might include new versions of the iPhone, with more features and a better camera and even a smaller iPhone Nano with less storage aimed at the lower end of the market.

But what if he does not return? That fear was behind the sharp fall in the stock price last night in after-hours trading and no doubt there will be further falls to come. Steve was evidently over-optimistic in his health bulletin last week and many will be worried that this latest e-mail downplays just how ill he is.

Some will wonder if Steve is understandably guilty of self-deception when he comes to his health. When he was diagnosed with pancreatic cancer in 2004, he told no one about it and tried to heal himself holistically for nine months before giving up and electing for the surgery that he so badly needed.

Who might succeed him? Tim Cook, the chief operating officer, has been his stand-in before and will run the regular Monday morning meetings of executives when they go over every aspect of the business. He is widely respected inside Apple but is not considered as a replacement for Steve. Phil Schiller, the head of marketing who has just given the Macworld keynote speech in Steve's place, is not thought to be enough of a strategist.

Intriguingly, the best candidate might just be the man who looks likely to give Apple's iPhone some serious competition this year. Jon Rubinstein left Apple in 2007 to become chairman of the smartphone company Palm, which announced the new Palm Pre to much acclaim at last week's Consumer Electronics Show in Las Vegas. He has engineering experience and has proved that he can handle rough times as he has helped to turn Palm round.

But let's hope that Steve is going to be OK and back in harness by the summer. If he decides to step down permanently, the tech industry and commerce in general will have lost one of its great leaders and innovators.

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