we've been blindsided in thinking that there would be an announcement! there wasn't one at all! totally bamboozled
PC version of GTAV was announced 9 months after it released on PS3/360. it didn't launch for another 10 months so there were 19 months total wait between consoles + PC. It's been 8 months since RDR2 came out on PS4/XB1 and still no announcement of the PC version!
unless we get an announcement this month or July then i can only assume that they are holding off so they can announce a Red Dead Redemption remaster for PS5/XB2 and the PC version. If that's what happens then I'd still expect the PC version to be held back until well after next gen version releases. The PS4/XB1 version of V released in November 2014 so the PC version was "delayed" by 5 months to April 2015. If the same happens then I would expect any PC release not to come out until early 2021. Rockstar got away with tempting/forcing people to double or even triple dip for GTA V. they probably made a fortune doing that shit so i wouldn't put it past the greedy bastards to try it again.
my guess:
RDR2 remaster - launch of next gen consoles in October/November 2020 or early 2021.
PC version - ~6 month after next gen version so April/May 2021 or October/November 2021.