I've been to the TH many times in regular passenger cars. You just have to drive slow and be careful.
I'd think the road work sign indicates something like a repair. Doubtful that they'd improve the road, as unpopular as that TH is. They get it back up to standard washboard and rocks, which constitutes maintenance.
Although they built a new beautiful Interagency visitor center there along 136 near Lone Pine, and are greatly improving 395 into divided highway with two lanes each way. It's possible that the American Reinvestment and Recovery Act may be providing funds, as I've seen on other highways.
Wonderful if they decided to pave all these TH roads and roadheads, with facilities, signs mapboards, etc. and whatever else. It's amazing what gets done as far as wilderness THs, lately. The contact here would be Inyo NF. If the rangers know anything!