There are a number of long trails in the USA that are surfaced and maintained, and even a few that are hard paved (the Paul Bunyan network in MN, the Silver Comet/Chief Ladiga in GA & AL). Can it happen in Texas?
IMHO the biggest driver the NETT has going for making it into a nice facility is the seventeen towns it passes through, some sixteen of which seem very enthusiastic about the future potential. B&Bs, guest cabins, cafes and campgrounds are already opening along the NETT despite some locally sketchy conditions.
It's a straightforward 58 mile ride from the Amtrak station in Dallas to the NETT trailhead in Farmersville, and a quiet 36 miles from the New Boston trailhead to the Amtrak station in Texarkana. Someday...