I don’t think that law is going to get changed by repeatedly breaking it.

I also don’t think it is a bad law. The probability of a pedestrian being fatally injured at 20mph is lower than at 30mph; older studies showed a nearly tenfold reduction; not sure what the figures would be now with the trend towards larger and heavier vehicles (and the offset by pedestrian-friendly design - EuroNCAP score for this). For residential and pedestrian heavy areas I think 20mph is appropriate.

It is also worth bearing in mind that several areas in the UK have already committed to 20mph for residential areas.

I think the more likely outcome is going to be changes to roads and enforcement.

Here’s a .pdf factsheet from RoSPA that looks at 20mph zones.