Keanu Reeves will appear on the Colbert Report on Comedy Central on Wednesday, December 18. From the schedule on Comedy Central, the same episode airs 4 time each day with the first airing at 1:30 AM. Depending on your location, that may change. You can check your TV listings for your locale here.
Note: Jimmy Fallon and The View, are both based in NYC and have not announced their schedule for next week so maybe Keanu may also turn up on one of those. Also if anyone hears anything about the Today Show or Good Morning America, also in NYC, please leave a comment.
Update: Jimmy Fallon and The View schedules posted. Fallon is reruns all of next week and Keanu is not on The View. That leaves the two morning shows.