Having played Deadfire like a maniac now, and already feeling the fear of abstinence, I reckon Obsidian sits on a diamond in the rough.
Here are my quick and dirty suggestions:
-Deadfire's interfaces and systems are for the most part spot on and great - reuse them in PoE3
-Naval combat can be dropped
-Either add a new map, like 33% bigger, with half of it being a coastline with an archipelago, and the other half being a huge overland continental thingie
-Start from level 1 again, with all new characters
-Pick some other climate and a few new cultures
-Add new music and monsters, plus a few new spells and abilities
-Just do minor class adjustments, no other system changed, really
And add a tighter story, more urgent and involving, perhaps personal.
Then stir and enjoy a fabulous PoE3!
Let's say, Autumn 2019, shall we?
What are your ideas for PoE3?
All I know that I want to see a PoE3 as soon as possible!