You do realise that your experience from 2014 is ridiculously irrelevant for what is happening in 2018? In 2014 they were in the middle of the refurbishment programme, where for any given variant of the 777 you could have had the new or the old J seat.

Now things are simple:

• if it's a 777-200ER - it's new business class (there are no more old business seats in the 772 fleet)
• if it's a 777-300ER with First Class cabin - it's new business class (there are no more old business seats in the 77W with P fleet)
• if it's a 787-900 - it's new business class (all 789s were delivered with new J seat)
• if it's any other plane - it's old business class

Yes, there *can* be last minute substitutions in case a plane has a technical problem, is delayed in its rotation. But typically that substitution would happen for a plane of the same type. It's very unlikely they'll substitute a flight that was planned with a First Class cabin (=new Business seat) by a plane that has no First Class (=and thus old Business seat).

There are routes where they make changes for given periods of time, and they do indeed know months in advance. For instance AF 008 during the summer months sees a 789 instead of a 77W (not a problem in this case, as both have the new J seats). But when they do know, they'll put that in the schedules and you'll know about it.

Refusing to fly AF in 2018 because you have had a plane substitution in 2014 is a bit like refusing to take the train because you don't like the smell of steam locomotives. Things do evolve.