I did a post a ways back asking about what people they took with hiking. I'm down to a month now before Colorado, and I think I've whittled it down to what I want where.
300mm f/4 L IS
1.4x TC
Tamron 18-270 (rental)
Sigma 8-16 (first time rental, if for some reason I don't like it, I'll go with my Tokina 12-24)
Extension tube set.
Monopod (I'm so used to using it as a walking stick, I think I'd feel funny without it.), with ball head.
Lightweight tripod, I'm going to share the ball head between it and the monopod.
I'm sort of sad to leave my 24-105 L behind, but the range, versatility, and lighter weight of the 18-270 makes it worth the IQ sacrifice. And it is a nice, nifty little lens.
I've started using a modular belt system and love it. I carry all my lenses on it, and am trying to jury rig a water bottle holder with a carbiner clip to be a holster for my tripod. I think I might get it to work. I'll add a typical lightweight daypack for non-photo related gear.
I'm also going to rent the 50-500mm OS for shorter walks around the campground and for car viewing. But I think it'll be a bit heavy for hiking (AKA-- trying to haul my large, flatlander butt up a mountain).
Can't wait. Hope I don't spend the first three days on my back with altitude sickness.