On the eastern end of US 175, I heard a rumor (can't remember where) that once more of Interstate 69 is constructed in Texas, US 69 between Jacksonville and Port Arthur will become an extension of US 175 to avoid confusion between Interstate 69 and US 69. Is this accurate, or is this rumor I once encountered an unsubstantiated one?
I've heard nothing officially about that. Would be a great idea to not have 2 major east TX highways with the same numbering. In a historical sense, it would be a partial full-circle as both US 175, and US 69 between Jacksonville and Beaumont, were part of the original TX 40 (before that designation was taken away, then used again later in College Station). It would also tend to help the case of US 175 being currently too short for AASHTO, even though the designation has been around for nearly 90 years, with little change in length in all that time.
The only thing I've heard in the last few years was by way of conversation with an official or engineer at the Tyler TxDOT office. He said there's been informal talk of possibly taking in the routing of TX 204 to extend US 175 further SE to connect to I-69; there was nothing specific as to an exact possible terminus, though (end at US 259 like TX 204 does, end with US 259 at US 59(/I-69) in north Nacogdoches, or a new routing somewhere else like Appleby (which would be the closest town to a further SE alignment from where TX 204 runs, if it continued east of US 259) so US 175 would have its own separate terminus on US 59(/I-69) without sharing an overlap with US 259). In any event, if any extension like that were to occur, discussion would likely take place regarding widening, as US 175 is used quite a bit by truckers and is considered an important hurricane evacuation route.
So, consider it rumor for now I guess, till we find out differently later on.