Red Dead Redemption 1, possibly coming...

I wouldn't mind playing RDR again. If it's on Steam, then I'll eventually get it at a discount. No rush for me though, because now that RDR2 is a thing, an RDR1 port feels a bit "too little, too late".

Plus, I'm not expecting any (significant) upgrades over the RDR1 versions that are already available for modern consoles.
But RDR1 had the Zombie mode when it was fashionable, would be fun playing that and if they really updated the gfx to RDR2 standard.
RDR1 on pc would be interesting, I'd probably prefer it since the snap lock aim mechanic on consoles is just easy to abuse.