Regarding Iris and Cilan, i have to admit they have lot of life and energy in their interactions with Ash and between themselves.As i already mentioned before after original trio i find BW cast have most engaging and enjoyable friendship established between themselves. From Iris snark and wildness being oriented toward nature relying on instincts, Cilan flamboyance trying to always look at things from scientific point of view and how for everything there exist logical explanation or Ash childish charm putting pokemon often on first place before anything else, clueless and brazen attitude they are delivering enthusiasm and lot of energy in their interactions fulfilling each other well.
As far as departure goes i imagine Iris will most likely be most emotional about it feeling down of having to abandon her friends. Especially since she didn't discovered true value of friendship until she met this guys being rather anti social and uncomfortable in bonding with humans due to negative experiences following her from childhood being treated as outcast.
And when she finally developed thrust toward others building solid friendship with Ash and Cilan i imagine it wouldn't be easy for her to just walk away.
While Cilan will probably try to keep cold head and remain stoic, suppressing his feelings while saying goodbye to Ash which was main reason he left gym in first place and learn about new ways of battling he wasn't aware of until he met him.
Or he could for all we know decide to stay with Ash and follow him to new region based on France dying to learn about their culture and learn more(eh if only we were that lucky).
Ash will be kinda sad and queer but overall i doubt their departure will hold same amount of tension and sadness like it happened with original trio split up for understandable reasons ill cover right away in response below.
Ash bursting into tears, Misty being on verge of crying being upset and disappointed over Ash initial carefree and Brock barely suppressing himself feeling melancholic was only sign of strong friendship, mutual understanding and admiration they build for each other and appreciation for everything his friends done for him helping him to stand on two feet, pass all struggles and emerge as stronger trainer. All three passed through many things together considering themselves like "second family "being only appropriate and within characterization to feel deplorable emphasizing on close bond they shared becoming much more attached and familiar within themselves than they were in Kanto..
Nonetheless your point about Misty leaving Ash again Hoenn doesn't help argument either because first departure from friends with who you slept, eat and did everything for long period of time(judging by 3rd movie reference, years)is always the hardest not being prepared for it. By than Ash got used to departures and his friends departing, and if i recall right Misty was still frustrated for having to leave Ash and others soon enough wishing to stick for longer.
So yes they cared, but leaned how to cope with leaving their friends and moving on.