Alright, so I'm wondering if, with the time, one can memorize the fretboard so well that he or she knows the note of every fret, of every string, even when changing to alternate tunings. Or is fretboard memorization an exercise in futility if you utilize alternate tunings a lot.

This skill might not seem like a big asset to tab readers, but I'm trying to learn conventional notation and sight-reading, so I was just wondering.

My first solution was getting a 7-string and using a capo to rip out pretty much any alternate tuning I wanted, for example BEADF#BE, put a capo on 5th fret you have standard, or if you have AEADGBE you have standard tuning and capo drop tuning (in drop tuning, F# wouldn't make much difference and you wouldn't have standard tuning anymore)... but back on topic, is it possible? Can fretboard memorization became second nature to the extent where even alternate tunings don't affect it?
Very doable, you just need to always remind yourself of your tuning and where you are on the fret board. It will take effort but it is plausible. Many people memorize every note of every string on standard, and I am sure people who utilize drop tunings very often also do the same for said tunings.
as long as you know where the notes are in standard you'll be fine, regardless of tuning
I see... what if your range of utilized tunings is drastic? Say, from standard to baritone and everything in between?
regardless of the tuning, the is still one octave of notes between the open string and the 12th fret. there are only so many notes in that distance.
So even if your tuning was 7 string A-C-G-E-B-C-D (what the hell sort of tuning is that? :P), low to high, the same patterns would exist, between notes, ie, a difference of one tone between A and B, while there is only a Semi-Tone between B and C, so knowing this is the way i navigate my fretboard

K, that make sense, or am i talkin out of my arse?
Ah, so it's just a matter of time and effort and in no means an exercise in futility.