My TOP list:
1. LSP improvements/quility. Now it doesn't work at all for big projects. (working on D11.3/D12). Refactoring doesn't work at all.
2. Generic Types improvements (more constraints, global generics, better work with interfaces (as/is support), better type infers, etc)
3. General IDE/Compiler/RTL/VCL quility. Better support for System.JSON / System.REST.
4. Ternary Operator (or make existing IfThen() as generic/magic intrinsic)
5. And the last one, Please, be more open for Delphi comunity - open Betas for all, open Roadmaps, Bi-monthly updates, etc.