Firstly, I agree they should have been made solo instances, but SE decided that the dev resources were not worth the investment...
Allow me to speculate, and do some comparisons to another exploit in recent history.....
If players willfully exploit this in some sort of 'protest' to get SE to do something, and they do make alterations...
I don't see them going with a 'scalpel' solution.
But rather a sledgehammer.
One that's quick, easy, and light on dev resource requirements but still adresses the 'problem'.
Think back to the launch of Stormblood.
We had rampant exploitation of game mechanics to avoid the intended AFK kick system in game.
Players were not logging out of the game, and the servers reached max capacity.
Other players trying to get in the game were stuck in hours long queues because people refused to get off and open up their spot.
I personally reported many people back at that time, one of which used to be on my friends list.
I know that GM's were taking action against these players, as I could see the effects on the person on my friends list.
That person was on a crafting class, in housing area, afk for greater than 30 minutes at a time.
After my reports, sometime after I'd see them offline.
SE did not do the resource intensive fix of revamping the afk kick system.
They went with the sledgehammer approach of just booting every single person off the server at the same time of the day prior to prime time.
This rectified the issue the first day it was implemented.
Queue numbers were still large, but the queues were progressing at a good pace.
This did impact legitimate players who were not exploiting, and trying to play at the times everyone logged off, but it did fix the problem.
Now, looking to the current exploit.
Like the afk kick exploits, it goes completely against what the devs intend for the system.
If they are forced to make adjustments to it...
I don't see them doing something resource intensive as retooling the instances to solo duties. (which should have been the initial fix).
But rather, I see them going with another sledgehammer approach...
What came to my mind was something like this...
A system wherein, if a player gets disconnected from the server during these duties, that player could be removed from the party and returned to the overworld.
Like the simultanious logout measures enacted during stormblood, this will impact legitimate players, but would copmpletely solve the problem of people exploiting disconnection to skip cutscenes.
I wouldn't like to see it progress to that level.
But I don't think a proper 'fix' to these dungeons will come from players massivly exploiting the game's systems.