Interesting debate - one thing I don't think that's been mentioned so far; if freestyle went in, then some other canoeing discipline or event would very liekly need to come out. There's huge pressure on Olympic organising committees to keep the numbers of athletes within a limit - so for a new sport to come in, a sport somewhere else needs to come out. There was a huge and long political fight to get slalom in hte games - after 72 it took 20 years, and most of the opposoition came from within the canoeing community i.e nations that were strong in flatwater, but not slalom, who didn't want to lose opportunities to win medals. So, assume there was sufficient political support for freestylye - where does it come from? Only from nations interested in winning medals, who don't already have a good chance of winning in other canoeing disciplines or sports. No support from the flatwater nations (e.g hungary, romania, italy, etc), WW nations (e.g france, czech, germany) may be interested, but not if it compromises slalom. Which it could do, although the argument of getting more use out of an expensive slalom course would be appealing to the bean counters. But do you really want to spend months and months getting good on a slalom course?
And to back up earlier comments - the olympics would raise the profile - at least once every 4 years - but I think would hurt the spirit of the sport. Closest comparison probably snow-boarding, which is counter cultural to most olympic sports.