doc for v2 (#2648)

README.md

@@ -77,7 +77,9 @@ frp also has a P2P connect mode.
 
 frp is under development. Try the latest release version in the `master` branch, or use the `dev` branch for the version in development.
 
-**The protocol might change at a release and we don't promise backwards compatibility. Please check the release log when upgrading the client and the server.**
+We are working on v2 version and trying to do some code refactor and improvements. It won't be compatible with v1.
+
+We will switch v0 to v1 at the right time and only accept bug fixes and improvements instead of big feature requirements.
 
 ## Architecture
 

README_zh.md

@@ -25,6 +25,10 @@ frp 目前已被很多公司广泛用于测试、生产环境。
 
 master 分支用于发布稳定版本，dev 分支用于开发，您可以尝试下载最新的 release 版本进行测试。
 
+我们正在进行 v2 大版本的开发，将会尝试在各个方面进行重构和升级，且不会与 v1 版本进行兼容，预计会持续一段时间。
+
+现在的 v0 版本将会在合适的时间切换为 v1 版本并且保证兼容性，后续只做 bug 修复和优化，不再进行大的功能性更新。
+
 ## 文档
 
 完整文档已经迁移至 [https://gofrp.org](https://gofrp.org/docs)。