Las Vegas can be expanded to 4 lanes. The original building plan called for 4 lanes, but supposedly NHRA asked SMI to hold off on the 4 lanes project for fear of obsoleting every other track on tour. I would be very surprised if Charlotte went "live" with 4 lanes ....
The Vegas plan was to have all 4 lanes side by side, with a slightly wider and higher wall dividing the two sets of lanes. The general plan was to only use both lanes during sportsman qualis and elims (not at the same time, they would run alternating pairs), and narrow it down to one set of lanes for Pro's, and if there is an oil-down, switch to the other lanes until the oil-down could be cleaned up to keep the program moving along.