The NETT is moving forward; reports from 2015 or even 2019 are obsolete. There's ~$20 mil up for grant proposals, and an estimate that total should complete the trail over the next few years in crushed stone, deck the remaining undecked tressels and install a prefab bridge over the Sulfur River.
This past year a trail festival was hosted by the towns on the 50 miles from Roxton to Clarksville and hundreds came out to ride some or all of it. Several teams of cycletourists have posted on Facebook this past season they rode the trail complete short a farm road detour around the Sulfur River.
Y'all ever find out a better route from Dallas to Farmersville?
The route I offered compares favorably in safety and scenery with the many cycle tour routes in other locales I see posted here regularly, and in fact with the Adventure Cycling route network and routes I see used by commercial tours. But no, there is no secret shaded, concrete, cycle-only path with lemonade stands every three miles between Dallas and Farmersville. BTW, the NETT uses a couple of miles of town streets in Paris (Texas!), and that will almost certainly remain the case even when the trail is 'complete'. If one just can not ride on any road with cars (and I know this is the case with some rail trail aficionados), that will be an issue.