There are many types of dayhiking. It depends on what/where you are shooting, distance/elevation gain/altitude, and what shape you are in. My fantasy kit is the lightest weight setup that I can find with very wide and very long options.
For example, my destinations are often high mountain lakes in bowls or the peaks above them in places like Rocky Mountain National Park near my home in Colorado. I'll scout my hikes on a topo map and identify some key things I might want to shoot along the way or at my destination. In the summer I might go 16 miles round trip and gain 3000' elevation in a single day with much of the trail above tree line at 11,000' to peaks above 13,000'. In the winter I might go half that far on snow shoes for a day hike. I'll easily take a few hundred photos during a 12-16 hour day, more with exposure bracketing.
So I try to travel as light as possible, but still have a wide option and a long option. I started with 550D but now have a 6D. I might like to try the 100D/SL1 as a second body someday.
Daylight is seldom an issue on a day hike so I don't need the fastest lenses - I'm usually shooting at f/8 or f/11. I tried using a single lens solutions with the 24-105L, but found I always shot at the extremes and they were never enough on the 550D. I like to perch on a peak and shoot the neighboring peaks a few to several miles away - it's a very different perspective than shooting from the valleys below so I will carry 70-200f4L and both extenders. Someday I might like to try the 70-300L. If I'm shooting a lake in a bowl from above or at lake level I'll need something pretty wide so 17-40L is often my second lens. With the 550D I brought the 8-15L along on occasion to go even wider and got some great shots. The rumored 14-24 sounds interesting for the wide end.
I always have a P&S on my pack strap for snaps along the way. During the climb I'll often stop and take a few snaps at every photo-op while I catch my breath since I'm not that young anymore. This works well in the morning since the mountains often cloud up in the afternoon and I don't have nearly as much energy on the way back down. I originally used a G series, then S95/100, now EOS M/22. I ordered the EF-M 18-55, but I really would like to try the EF-M 11-22.
One suggestion I would make is to get a real pack if you plan to do some serious dayhiking, not a camera bag/pack. And get a pack larger than you need just to fit your gear. My gear would easily fit in a 30 liter or smaller pack but I carry a 45 liter pack and use the compression straps to cinch it down. Larger packs have better suspension systems to carry the weight and your camera gear is much heaver than a sleeping bag and pad. Your body will appreciate it and you will have a much better day. I usually carry a Gregory Z45 with camera gear, ten essentials, food, drink, and enough extras to spend the night in an emergency. It feels a lot lighter than a smaller pack fully loaded.
I use a similar philosophy even when hiking mountains in other states at lower elevations. I pleased with my current setup, but there is always something else to try. Suggestions?