Would a tripod be useful for the views at sunrise?
Depending on the time of year you are going, you may not make it to the sun gate for the sunrise. We were the 2nd group through the start gate on the final day of the Inca Trail hike (it opens around 5am if i remember correctly). We made pretty good time to the sun gate (even though we forgot to pack head torches...not fun navigating that trail without decent light!) and we missed the sunrise...it wasn't very good weather for it anyway though. We went at the end of July.
I took a gorilla pod...didn't use it much. My cousin brought his full size tripod, and he used it less... Having said that...if I did the Inca Trail and Machu Picchu again, then I would take a tripod...not for the sunrise at Machu Picchu though. I would take it for taking photos at night at the camp sites...the stars are amazing! (if you get a clear night - we only had one)