Comment by Y-bar

Maybe.

But there is already a known pattern on how to handle this which I was taught (before the original iPhone even) in university CS studies:

If the manner of entering credentials has to change,

Then on first entry, offer the old method,

And, because you now (temporarily) have the plaintext credentials, you can now inspect it and test if anything need to change for the future,

And then set a flag, or require user action , or just re-encode, to use the new method as inspection determines.