Im not getting a good feeling from what's happening at Sun since Oracle took over,lots of good people seem to have left, Solaris now needs a support contract to use after 90 days(read the download T&Cs)who knows how open MySQL will be? oh well there is always open Solaris and hopefully ZFS will go into more OSs likse it did into freeBSD
I personally get a bad feeling from ALL CLOSED STANDARD COMMERCIAL PROPERTY software.
At the end of the day Oracle's #1 job is to make money, databases ,applications,hardware ,software and services are all tools to achieve this
postgeSQL looks like the likely candidate due to is support in apache hadoop and even a variant in commercial products like Greenplums data warehouse cloud
anyway here is a spot to put Oracle to postgreSQL links, I think downreved ORA to latest PG is a doable migration. Just a straight DB is good, PLSQL makes it harder but there are conversion tools
Oracle to Postgres Conversion - PostgreSQL Wiki
Orafce Project - Oracle functions
Oracle to PostgreSQL