I had the privilege of seeing Salopek announce the project at the Knight Civic Media conference, and based on his presentation I can tell you that he is not taking this lightly. This isn't a project that he decided to do on a whim without evaluating the risks. This is a very well-planned, calculated project that desires to not only be fascinating, but also to make a statement on journalism itself. He won't compromise the integrity of it. Of course, there will be people aiding him along the way out of necessity (translators, guides, etc), but I guarantee you there won't be a helicopter or truck involved.
Out of curiosity, I skipped through his talk. He says he will leave Vladivostok on a research vessel and cross the North Pacific that way.
If that is not the proverbial "truck", I don't know what is. I don't blame him, but National Geographic/BBC should really know better than publish such misleading maps.
I would love to read the story of someone who walked from Siberia to Alaska via the shortest sea crossing possible. But above Magadan, there are no more roads. And the Kolyma highway to Magadan is considered a major adventure already, with only a small window where the rivers are low enough to be crossed by motorcycle (and therefore, man).
I'm not saying this can't be done, but it looks like a serious arctic expedition to me. Which I kind of doubt he will do. This is probably going to end like usual. Helpful Russian truck drivers take him with them for as far as they can go, then (Mommy!!) a helicopter shows up...