They gonna remove the flash-client, and the possibility to use those other prereq?
Well, flash is dying and will be gone in 2020 across all websites. So until then, Fizzer could just leave the legacy client up. However, flash won't get the new features etc.
If you use a template created in flash, then you can still get the prereq's (I think). Through be careful editing that template.
min level, max boot %, 1v1 win % and one more as far i remember)
Only those 3 atm.