CRTC relaxed its regulation of music formats in recent years. Before then, CRTC approval was needed for any major format change. (Some labels, such as "Adult Contemporary," were applied broadly allowing for a decent amount of wiggle room.)
Classic Rock would be an unwise move. There are two Classic Rock stations from Detroit that boom into Essex County. Such a move would also step on the toes of classic rock-leaning Variety Hits station, 100.7 Cool FM.
Mainstream Rock is the more likely possibility. Blackburn programmed such a format on 100.7 in Windsor (and 95.1 in Chatham-Kent) for a number of years.
I would not expect any sudden, major changes at 95.9. I think a wait and see approach will be taken to see how much traction 88.7 is able to gain with country music. The playlist on 88.7 is well structured, but right now, the station is little more than a glorified jukebox.
I would hope either 96.7, 100.7 or both are repositioned a bit musically to attract disenfranchised 93.9 The River listeners. The 89X audience was too small in its final days to worry about. (Many 89X listeners jumped to WRIF years ago on both sides of the border.)
I suppose an additional possibility would to be flip 95.9 to a Modern AC / AAA blend very similar to what The River programmed while keeping all other stations in the cluster as-is.
That raises another question - should 96.7 continue to play a ton of teen pop currents & recurrents? Seems to me they are missing the Hot AC sweet spot, especially in light of 93.9's format change. Many artists are now shared in common with 93.9. Wouldn't it make more sense for 96.7 to reposition itself as a true Hot AC that is less aggressive on current music?