With slim, widescreen machines promised as the "MacBook" replacement of the iBook for May or June according to rumours, possibly in several colours and with DVI-Out connectivity, there will be a landslide of customers towards Apple, unless further hardware problems emerge (a possible source of which could be Apple's inclusion of flash memory, between hard disk and RAM in the sequence of memory elements; there is no precedent for this in any hardware sold by the company). The next release of the operating system, Leopard, will be well placed to steal away further market share, especially if Apple manages to keep the footprint small (an area where Vista is especially vulnerable).
At the other end of Apple's business, there is a risk of losing mp3 player market share unless they can revitalise their range with colourful models to mimic the appeal of the iPod Mini. Note the negative knock-on effect this could have on their iTunes Music Store. France has taken a lead in asking Apple to unlock iTunes for other mp3 player manufacturers, and further countries are likely to follow. In fact, Apple's losing mp3 player market share may force such a move of the company's own accord to keep the store alive. I very much doubt it will come to this, but it is clear that Apple has to continue remaining competitive on price and innovation, especially since in spite of their promotion of podcasting, this has remained a niche market.