Revise README for PicoXLSX v4.0.0-rc.4

Updated README.md to reflect the new pre-release version and changes.

Author: rabanti-github

README.md

@@ -9,10 +9,12 @@
 
 ## Pre-Release v4.x
 
-The pre-release of PicoXLSX is now available as [Nuget Package](https://www.nuget.org/packages/PicoXLSX/4.0.0-rc.3), version **4.0.0-rc.3**.
-Since PicoXLSX v4 is now based on [NanoXLSX](https://github.com/rabanti-github/NanoXLSX), and there are breaking changes between PicoXLSX v3.x and v4.0.0-rc3, please see the **[Migration guide](MigrationGuide.md)**, to migrate applications from v3 to v4. Please feel free to open issues, in case of problems with the pre-release.
+The pre-release of PicoXLSX is now available as [Nuget Package](https://www.nuget.org/packages/PicoXLSX/4.0.0-rc.4), version **4.0.0-rc.4**.
+Since PicoXLSX v4 is now based on [NanoXLSX](https://github.com/rabanti-github/NanoXLSX), and there are breaking changes between PicoXLSX v3.x and v4.0.0-rc4, please see the **[Migration guide](MigrationGuide.md)**, to migrate applications from v3 to v4. Please feel free to open issues, in case of problems with the pre-release.
 
-There will be possibly further adaptions and additional pre-releases before the final release.
+rc.4 is planned as **last release candidate** before the final release. If no errors are discovered in this version, the final release (v4.0.0) will have this code base. The v4 release is planned for **end of February 2026**.
+
+See also the wiki entry for some thoughts: [From Monolith to Modules: Why NanoXLSX Finally Broke Its Own Traditions](https://github.com/rabanti-github/NanoXLSX/wiki/From-Monolith-to-Modules:-Why-NanoXLSX-Finally-Broke-Its-Own-Traditions)
 
 ---
 
@@ -125,3 +127,4 @@ See also: [Getting started in the Wiki](https://github.com/rabanti-github/PicoXL
 ## License
 
 [![FOSSA Status](https://app.fossa.io/api/projects/git%2Bgithub.com%2Frabanti-github%2FPicoXLSX.svg?type=large)](https://app.fossa.io/projects/git%2Bgithub.com%2Frabanti-github%2FPicoXLSX?ref=badge_large)
+