Well I will chime in even though I am a flatlander
After 11 hunts in 13 years out west, 9 of which were above 12,000 feet I can tell you that good rain gear (Goretex), wool socks, wicking undergarments including your underwear, and layers that you can shuck on/off as you heat up/cool down will get you through 99% of the time.
I am planning a hunt for Rocky Mountain Goats in 2012 and will most likely drink the kool-aid and buy some lighter-weight true mountain wear to go along with my polypro and wool undergarments because weight is going to be a huge issue on that hunt. I will say after attending several wilderness medicine courses as part of my job the last 5 or so years there are 3 things that will kill you in the mountains: falls, weather, and cotton
IMO cotton is great for warm weather, out the back 40 hunts, but in situations where you might have to spend the night out in cold, wet conditions, it's thermal properties are zero compared to synthetics that dry quick or wool which retains it's thermal properties when wet.
Good luck! You are gonna LOVE elk hunting. It is addictive and spellbinding and will leave you with the 1000 yard stare long after your hunt is over