This is like saying you're concerned about the automobile's impact on the trolley bus. Telecommuting has an impact on the amount of people entering downtown, but it isn't the root cause. Downtown is a pain in the ass. Parking is always difficult. If you're looking to open a business, services in downtown like banking are existent but poor.

Compare that to the biomed corridor running down Route 9. You're off the highway and pulling right into work. It's not telecommuting that's killing downtown, it's that downtown is an inconvenient place to do anything.