The relevant section is reproduced below:
The notification does not explicitly say that users should stop using Aadhaar for eSigning after July 31. If extra charges are going to be waived for those migrating by July 31, it means that extra charges would not be waived for those who continue to use Aadhaar for eSigning after July 31. It seems to suggest that UIDAI expects there to be people who would continue to use Aadhaar beyond July 31.
It would be good to have clarity on this matter. The question is:
Will VID be compulsory for eSignatures after July 31 2018 or can Aadhaar be used by paying an extra amount per transaction thereafter?
Of course, irrespective of what we think, the interpretation of ESPs / CCA / UIDAI would be final.