Can expdp be piped directly into impdp, without intermediate files?
As @mutap stated in the comments, you can expdp/impdp over the network.

Technically, you will be doing the DataPump export and import over a database link without the need for an intermediate file.

Bash PIPE is not needed.

Example:
https://oracle-base.com/articles/10g/oracle-data-pump-10g#NetworkExportsImports