The current thinking around resolution of film is that SUper 8 can scan up to about 1080p; S16mm 2k-4k, and Super 35mm anywhere from 4l to 6k-8k depending who you talk to.
Kodak tend to adjust their numbers each time a new digital camera comes out..
Film is simply captured differently to digital, so it's difficult to pull a definitive resolution number from it. Also, some will tell you that even if the actual image itself hits a point where scanning at a higher resolution doesn't increase the quality, the finer detail of the grain can make it appear to be at a higher resolution.
It's all a bit subjective.
At the most basic level - the answer is yes, you can scan 35mm film into around 2k-4k resolution to create a Blu Ray release. One would imagine that most super old TV shows would require some amount of digital restoration, and also some careful re-framing to adjust from 4:3 to the 16:9.
I started watching one of my favourite shows from the mid-00's that was shot on S16 the other day and realised that it was unlikely that it will come to Blu Ray because 85% of the framing would be impossible to adjust for 16:9.
If I remember correctly, the DP for Scrubs tended to frame for 16:9 safe, even though the first seven seasons of the show were broadcast in 4:3 - I imagine there are many others who have done the same thing, meaning they're easier to re-frame and bring to Blu Ray.
Digital isn't great as an archival format since whatever the film was shot at is the resolution it'll always be - sure, you can blow up 1080p to 4k and with some refinement, it might even look OK but there'll never actually be any more detail in the 4k version vs. the HD one.
You could say the same about, say, Super 8 or Super 16mm.. The reason digital is a bad archival format is that it has no longevity.
Whereas with film, you can print something onto film, bury it in the ground for 100 years and come back and scan it in at full quality - with digital you need to constantly update your LTO tapes (as in, ever 2-3 years update the tapes and systems) and make backups of your backups in case of data loss...
By Kodak's numbers, digital archival costs ~11 times more than film...