Well, memchunkhax 2.1 wasn't technically patched iirc, but it was made near-unworkable due to canaries being added into the kernel11.
In addition, the process9 checks mean that even with an arm11 kernel exploit, we won't be able to downgrade. There are already a number of arm11 exploits that have been discovered privately (my favorite being
slowhax, which takes over an hour to execute). However, the developer has decided not to release these exploits yet as he wants to finish an arm9 exploit before he releases anything.