The Houston Chronicle reports today that TxDOT has changed plans to route the highway through rural areas to the north and west of Houston, instead using existing US 59 (the Southwest and Eastex Freeways), the 610 Look (West Loop and North Loop), or the Grand Parkway (Texas 99). Through most of the state, US 59 will become the new I-69, and while much upgrading is needed, a lot of this highway is already up to Interstate standards, particularly in the Houston area.
However, running the new "I" either straight through on US 59, or worse, putting it on 610 (the busiest highway in Texas, and possibly the U.S.) seems to me to be a bad idea. If this gets Grand Parkway completed, it will be a much better routing, in my opinion, although the new road will quickly become as developed and congested as the others. Still, it is far enough on the outskirts of the city to avoid running the Mexico to Canada traffic into the Bayou City's rush hours.
I-69 already exists from Indianapolis to the Canadian border in Michigan, and upon completion, this will be a major trade route from Mexico to the markets in Canada such as Toronto, Montreal, London, and other major cities. For more on I-69, check out the following links:
I-69 Article on Wikipedia
Snopes debunks a sexy I-69 myth
Houston Chronicle article about the routing of the highway