I feel that boards will be super-disappointed if 'no-adc' bot actually happens

For multiple reasons.

• popular opinion on boards is that juggs should be allowed to be the team's main carry (i.e. the farming botlaner). Meanwhile, juggs are possibly the hardest class to put there. Why?
  • team's main carry == the most reliable source of damage. Juggs are DEFINED by lack of reliable gapcloser. That's a contradiction, constradictions are hard to solve.
  • juggs are very tanky. Depending on meta, they are the tankiest or second tankiest class (sometimes their sustain gives more than tank's resistances, ATM it doesn't). Putting a tanky champion as team's main carry allows compositions that completely invalidate assassins and since assassins are usually super-popular, Riot won't allow that to happen easily.
• the first class to be allowed bot was cofirmed to be mages
  • mages, typically, have more/more reliable CC than ADCs. Replacing adc with a mage yields a heavy-cc composition, against which fighters won't likely do well (more kiting), especially the oh-so-loved-by-boards immobile fighters (read: rylai meta all over again, only worse)
• the second will probably be skirmishers (although that's my guess, it feels reasonable)
  • fighters often can't duel them. Again, that yields compositions that suck for enemy fighters.
• balancing a champion both for duo and solo lane is a pain/barely possible
  • fighters are typically played for their 1v1 proficiency. If some of them were to be pushed into duo lane instead, existing playerbase is likely to be seriously disappointed. There are a few hi-elo fighter players who would like to be the main carry to have more impact, but simple truth is that 99% of playerbase plays fighters for 1v1 brawls. RIOT won't easily risk losing that.

the TL;DR here is that if fighters will ever be allowed to bot, they will be the last class to get that possibility (tanks and enchanters IMO never will), and fighter players will fucking hate the transition period (that can take like 3 seasons).

Now, I don't mind that (despite having mastery lvl 6-7 on several immobile fighters, and pretty much never playing ADCs), but mark my words, there will be even more fighter salt flowing here on boards in second half of S8 than it is there now, and you will miss ADCs.