Are there any news regarding the security concerns of the software, now that the MK4 is released?
Coldcard Mk4 version not officially released yet, you can only reserve it aka pre-order it... and it's been like this for a long time.
I don't think there are much concerns because they finally decided to be honest and admit their firmware is not open source anymore, but you can still verify it and see what it does.
Not sure what you mean when you said ''software'' but I suspect that new version will only have similar and improved code like previous versions.
Colrcard is not my favorite hardware wallet, but I consider it much better option than ledger, safepal and similar junkware closed source devices.