I find an answer that recommends to convert in zip, change the version in de xml and zip again, but its not working. I tried with my own projects before change anything and SAS is unable to open it.
The process was: I convert to zip, extract the files and then covert again with 7zip and rename to .egp, and SAS is unable to open the project.
The XML schema changes between versions. You can't just change the version number and expect it to understand what is contained within. The XML schema is not public so you can't fake it easily. If it was public, you could possibly use XSLT but I have never found a schema for EG and was told it doesn't exist. Hence, changing the version number is useless and should always result in an unreadable file (barring a simple, simple project and a lucky guess).