Both Johnson and Yelchin have been name-dropped by fans in the months following the reboot news, especially Johnson as Kick-Ass saw him basically playing a powerless version of Peter Parker. He certainly had the awkward teenager act down, but I personally didn't buy his heroic side, especially not when up against Hit Girl. Johnson seemed uninterested in the role when asked by Movieline, but he's at least been tempted enough to try out.
Yelchin has proved he's not daunted by iconic characters, as he tackled Pavel Chekhov and Kyle Reese and managed to leave his mark. I liked him in both films, but does he have the charisma to carry a film on his own? It's one thing to be a really likable sidekick, but a superhero requires a certain kind of power.
The LA Times notes that none of the seven actors have screen tested yet, but are now expected to. No one expects the list to stop at just these seven, though. I wouldn't be surprised if casting follows Captain America's, and we end up with someone completely off the initial radar. Who is your pick to don the red and blue webbing?