The existing voltage dividers should all be fine with 3.3V. And the pull-up you added for Arduino-RX is still harmless but also not required.

Ideally, those voltage dividers should all get adjusted from 10K/10K to 20K/10K. But the existing 10K/10K should continue to work.

No risk in leaving as 10K/10K as you say, other than that the inputs might be less reliable than they would be with 20K/10K. Really though, I expect everything to just work as it always did. The 3.3V empeg I2S would no longer need any resistors.

Cheers