Its not clear if o2 will have the rights forever, but they certainly have the high ground with the Palm Pre under their belt also.
They wont, It was never the plan to be one company per country. The deals made were just exclusive rights for launch and a period after (approx 2 years). I am sure each company around the globe will be offered the right to renew their exlusitivity but you can bet it will be a hefty some. Now the iphone is well established and has features that enable it to function under most networks finally you will start seeing it on other networks maybe this year even. There are some pretty cool android phones on the way as well.
Android is nice, it just gripes me it is not multi touch. The new palm device which is a baby brother of the palm pre looks quite sexy as well.