I was told I am supposed to PCS before I go to AIT in January. My company is telling me I am going to Ft. Knox in November and then I will go to AIT in January. Can they do this?

Probably.
Can you change it? depends!

What AIT? Why are you PCSing? are there slots for your new MOS at Knox?

PCSing my brigade as a whole is moving to Knox. And 46Q AIT. My slot at Knox is at my old MOS 88M

Then why WOULDN'T you PCS with your unit?
are they just going to leave you where you're at now twiddling your thumbs?

You MIGHT be able to transfer to another unit where you're at, but honestly just don't unpack when you get to Knox..

Well the reason why I am not PCSing to Ft. Knox with my unit is because my AIT is like 5 months away. So G1 at Ft. Hood is just sending me to another unit on post until my AIT starts. Like your saying about the whole unpacking thing. Wouldn't make much sense to send me to Knox for 2 months then to AIT then to another new post.