I don't know if the NPPL will disappear but I suspect the biggest obstacle might be the lack of a formal medical.
Though as one can fly on a NPPL using a JAR-FCL medical one could argue that, if such a situation arose, anyone who wanted to utilise an IMCR on a
NPPL would have to be able to pass the JAR-FCL Class 2 medical.
In this hypothetical world it would probably also require an increase in hours required for the issue of the IMC rating to cover gaps in the NPPL syllabus.
Whatever, the remit of what the NPPL does and does not allow is currently home based so anything is possible at the moment, but it is worth bearing in mind what the thinking behind the NPPL was. I'm not convinced it was ever envisaged that it would or should include IFR/IMC privileges.