Yeah, every single release since then has had work done on scaling Postgres up on a single machine. They have been working on eliminating bottlenecks one after another to allow it to scale on crazy numbers of cores.
I've seen benchmarks on the -hackers mailing list with 88 core Intel servers (4s 22c) in regard to eliminating bottlenecks when you have that many cores. So even if it's not 100% there yet, it will be soon.
On highly concurrent PG systems by when using parallel queries you are sacrificing throughput for better latency. You really don't want to use more than a fairly small number of workers per single select.
Not a problem at all if you provision your server properly so you aren't IOPS bound, though there are plenty of databases which simply won't fit on NVMe drives, so in those cases, yes it could still be a problem.
Not likely to be a problem if you have FusionIO drives. Likely to be a problem sooner or later on everything else. A definitive recurrent issues on all cloud providers and NAS/network drives.
I've seen decent enough scaling on 8 socket servers. There's still some bottlenecks if you have a lot of very short queries (because there's some shared state manipulations per query & transaction), but in a lot of cases postgres scales quite well even at those sizes.
I've seen benchmarks on the -hackers mailing list with 88 core Intel servers (4s 22c) in regard to eliminating bottlenecks when you have that many cores. So even if it's not 100% there yet, it will be soon.