That's not true. I, first of all, have no doubt in my mind that MitsuAi will become canon. Gosho has set up a trail for it and it's not like Haibara has anything to go back to as an adult so why the heck not? XD It's not like anybody expects for them to be in a relationship at age 7 anyways.
Then for Conan and Ayumi I am stuck on the theory that Gosho will separate Shinichi and Conan and Shinichi will go back to his normal life while Conan will stay a member of the DB. That would explain why Ran felt lonely without Conan when his "Mom" came to get him. To show that it would be very very difficult for things to go back to normal if Conan left. It was setting a trail and in my opinion kind of foreshadowing Conan's possible permanent existence. Which would mean Conan could grow up with Ayumi, fall in love with her, and... possibly repeat the entire thing with Ayumi as his new Ran.