Driving in the EU if there's no ****** deal - GOV.UK
This is the government's official statement.
An extract:
The 1949 convention IDP lasts for 12 months. After 28 March 2019 in the EU, a UK issued 1949 IDP would be recognised in Ireland, Spain, Malta and Cyprus.
The 1968 convention IDP is valid for 3 years, or for however long your driving licence is valid, if that date is earlier. The UK ratified the 1968 convention on 28 March 2018, as a part of our EU exit preparations. The 1968 convention will come into force for the UK on 28 March 2019. After 28 March 2019, a UK issued 1968 convention IDP would be recognised in all other EU countries, plus Norway and Switzerland.
So this confirms that the 1968 convention version is not in effect till 29 March 2019.
I agree that at present the IDP is probably checked infrequently if you are driving somewhere that requires it.
However given the possibly acrimonious departure from the EU I wouldn't be at all surprised if EU police forces would as a consequence focus on the need to have such ...