I'm yet to play DS3. My first experience of the Soulsborne genre was Bloodborne last year, then the Dark Souls remaster. Played Dark Souls 2 for the first time last month to get in the headspace for Sekiro. Replayability isn't an issue for me as there's too much media around that I want to try for me to even so much as rewatch a film or TV show, let alone replay a 40-hour game. My main concern with Sekiro is that I can be shit at these games so the lack of multiplayer may see me hit a difficulty spike that renders the game unfinishable, which would be unfortunate. Definitely wouldn't have finished any of the Souls games or Bloodborne without the ability to summon. Very keen, though. I rarely buy games first-day but, as I say, I want the experience of playing a From game without the crutch of wikis and walkthroughs to lean on if shit gets confusing or hard.
Pleased to see in one of the previews I watched that they reckon the parrying system is way better than in Dark Souls. I always had a bitch of a time with that, to the point that I don't think I parried once in my playthrough of Dark Souls 2. Apparently it's quite important in Sekiro, though, so makes sense they'd make sure the mechanic plays tightly.
Gonna be weird as fuck playing a From soft game with verticality. That alone is going to offer up tons of new avenues to fun and frustration!