Unlike some (and i gather theres quite a few) im actually still enjoying EU4 quite alot, i play it more often atm than any other PDX title -for now atleast-. so im not too bothered if theres a new EU coming or not, however i can see why PDX wanna keep working on EU4 considering theres so many dissenting voices saying they dont like this or that, so i see the sense in them trying to 'fix' the main issues before they jump ship. Kinda like CK2, they kinda stopped development on CK2 when the feature-creep got too much but also when they felt they could leave CK2 and be proud of where it ended... and i dare-say CK2 ended at a perfect time, they fixed the vast majority of the performance issues that was introduced as the years went on (Reapers Due), then added some requested things like artefacts and societies and ended with Holy Fury which completely overhauled the Crusades and overhauled pagan religions and added a huge number of other things which left the game at a perfect place to end (ofc, then SnowCrystal released the iron century mini-thing that was so well received i remember doom and gloom being said when it was revealed they were going onto another project -i think it was Imperator?- ) but anyways, i can see why they are still swinging at EU4 at this point, its a great game theres just... issues that need addressing, but sadly with all the time and work thats went into it they are kinda limited on what they can to do solve the issues. but i remain extremely interested in where they take EU4 and dont see the need for EU4 to end just yet.
So yeah, all in all i wouldnt mind an EU5, id prefer Vicky3 first in all honesty, but if they took a whack at EU5 first id kinda understand. Victoria 2 is more of a cult Classic at this point whereas EU4 was one of their most successful titles.