Also.. what evidence are people using to predict Chris will leave by the end of the year? I don't see it myself. You're making predictions like The Sun, but without the means to print it for three million people to read.
I was offering my own personal opinion hence I didn't feel the need to present evidence.
However, if you wish to know my reasoning for arriving at this opinion then here it is. The Breakfast gig, history shows, has a shelf life. True, he could buck this trend and go on for years more. But I suspect that he knows the gig has a shelf life, as will his agent manager etc, and they will have been planning his next career move for some years, as I doubt that after the Breakfast show they want his career to stagnate or go backwards as it could be argued happened to many of the previous Breakfast hosts over the years. The 'softening ' of his image has been carefully stage managed in recent years, giving some very high exposure - X Factor, Live Earth, the books (and subsequent TV interviews) and now of course, in what is his fifth year as host, just 5 months or so away from the record, the C4 TV show, which according to a couple of reviewers I've seen who would normally love to slate him have grudgingly admitted that the show is actually quite good.
Putting all this together, my OPINION is that, being a top professional as he is with professional pride, he would want to bow out on a high and choose his departure date and not be shuffled out, and once the record has been broken, assuming the show is still bringing in high ratings, there would be little else for him to achieve in the slot and it would be a good time to move on. I still reckon he'll mix radio up with TV, but in what format remains to be seen.