My advice would vary depending on your circumstances. If you are a frequent traveller, who uses hire cars a lot in different countries, then absolutely yes get an IDP (making sure you get the right one for each country as reportedly different versions exist).
If average traveller, then hang fire till it becomes more clear.
Key dates would be this week - if the Cooper amendment passes, then an extension becomes significantly more likely - I suspect no deal will not occur, but anything can happen in British politics at the moment.