Longest serving pro remaining is Karen, followed by Giovanni (2015), Katya, Neil and then Gorka who all started in 2016, unless you count Luba who I remember seeing in group dances in 2016 as well.
To me it seems like Gio has outgrown Strictly and seems to be doing well outside of it with his own shows and fragrance brand. Not that this means ilhe will leave of course.
Michelle has been a pro for 2 years, but hasn't had a partner yet so I hope she gets paired with someone in the next series, otherwise she will go the same way as Chloe Hewitt and Cameron Lombard.