This is nothing new. It was supposed to launch last year at SEMA (November) in Vegas. Keeps getting delayed. Will see if it actually happens.
And yeah, GRC is not coming back. All of the teams abandoned it, GRC was going to try to go to their new "Gold class", only 2 cars signed on as far as I could tell. They also owed money to a bunch of venues. There were many internal issues going on with GRC, which is probably part of the reason Subaru and Volkswagen leaving. I loved GRC, but if the teams all want to get out, then nothing can be done. ARX in 2018 is kinda a test year i think. Soft launch. In theory they should have a more full schedule next year. It should evolve into something just as good if not better than GRC, but only time will tell.