I would love for the AR15 to become non-restricted, but I don't think it will happen.
I am a bureaucrat (don't hate - I'm not federal and I work with highways) who has to deal with political nonsense every day. I can't see any party standing behind this position because it will cost far more votes and support than it will generate.
No party will support this idea, because the political visibility of changing the classification of this rifle is just too juicy for the opposition to not use against them, and the stance would ultimately cost them votes and support. Show a photo of an AR15 to an average joe turkey and you can be sure their immediate reaction will be that it is bad and evil. That is all it takes and all that matters - you think the average joe turkey is going to educate him/herself about how the looks of a rifle doesn't make it any more or less dangerous as their grandfathers old hunting rifle? Their initial reaction is what counts in the world of politics.
Unfortunately, I think your ultimate solution here is time. Eventually the ar-15 will become dated, and new better rifles will take its place. When that happens, it will be hard for the politicians and policy writers to keep up. Hopefully these new rifles will become more established and therefore more difficult to restrict without the risk of backlash and lawsuits.
It is all about optics - I think the Tavor is a good example - I think it looks like a futuristic death machine and perhaps more evil than the AR15. If there was more of them around, and the public knew you could drive around with one in your car, you can be sure there would be a lot more pressure to restrict it or ban it. But since there is no visibility on the Tavor, and therefore no votes to be made, nobody seems to care.
Keep in mind the responses to the majority of the letters you write are being drafted by some low-level bureaucrat. Basically what [the bureaucrat] does is write a simple fluff letter with no content and no commitment (for the politician's signature). 99% of the time the bureaucrat doesn't even know the opinion of the politician they are writing the letter for. We call them PFO's - which stands for "Please F*** off."
Sorry I usually just lurk - but felt like writing something tonight. I want things changed just as much as anyone, but being in the system and knowing its limits, I can't see it happening. I wanted an AR15 but I settled for a SU16 with pistol grip and LAR mags.