Show me some credible source that says I35 will be a toll road.
Neither your map nor your link says that.
The Trans-Texas Corridor (TTC) is a proposed multi-use, statewide network of transportation routes in Texas
that will incorporate existing and new highways, railways and utility right-of-ways. Specific routes for the TTC have not been determined.
Keep Texas Moving
Also:
Federal Highway Administration
Credible enough for you?
And in reference to your post#91, re-read the article, especially paragraph 7.