This is wrong headed on several levels, it strains believability that more than one person considered this course of action and thought it was a good idea.
You're adding new AB that require R9 characters to earn max rewards, replacing old AB that could be maxed out by R3-R5 characters. Additionally, the new AB do not offer the same rewards as the old AB, yet you're presenting this rotation as though it won't have any net difference in our rewards. Ridiculous.
The time, effort, energies, crystals, and money investment in getting one character to R9 are huge. Two or three characters to R9 takes more resources than some people have earned in total!
Also, look at the players who've already invested in squads to max out the old AB. Grind, upgrade, fight, win, 3*, hooray! That effort/investment is disrespected by your plan to rotate out old AB. This rotation idea is a very loud signal to the players that you, Devs, do not respect our time, effort, or investment in your game.
Insulting, disrespectful, and utterly wrong headed.