Radioprogramas del Peru has reported that UNESCO has weighed in on the celebration plans and as a result, Peru’s government will be restricting access of journalists and the planned fireworks display at the ruins is being canceled. Most importantly the concert will not be held in the Citadel. Still no official word on where it will be relocated to.
In any case it’s a good bet whatever the festivities turn out to be, there will be large screens set up in Cusco’s main plaza to see it.
Also people around the world will most likely be able to tune in on Peru’s national public station via the Internet: http://www.tvperu.gob.pe/index.php (Click on “TV En Vivo”)
Also, look for updates on the Machu Picchu 100 Anniversary official site.