Have you got those sales figures Gruoso? I will be very suprised if Nikon is anywhere near canon in market share.
It is going to take a lot to knock canon off its perch, especially in the entry level market of DSLR - this is an area where herd mentality rules just cruise around some of the scrap booking sites etc they are pretty much all canon users as they don't want to be the odd one out canon rebels/xti's rule this market with about 90%+ canon users.
Pentax can produce a camera for the same price as the canon xti, with better build quality etc (Oh yeah Pentax already have) and markets such as the scrapbookers will still flock to the canon as is currently being proven.
Take a look at sites like
The Best Scrapbooking Supplies On The Web - Two Peas in a Bucket and check the photography discussion board - these girls take there photography seriously and not many newcomers want to cross the canon brigade who all LOVE their Canon - although there is a dedicated group of Pentaxians on there - with my wife flying the Pentax flag every now and again.
People may be impressed by the D3/D300 - but I guarantee you the Nikon D40 outsells both of them put together.
Likewise the canon's for every Mk3 owner there will be approx 10000 xti owners who wouldn't have a clue about focusing issues - cause as far as they are concerned they have a market leading pro spec camera in canon.
Pentax are doing the sensible thing and slowly building marketshare in the entry level and hobbyist market - and they are doing it very well IMHO.