If you want to move to another DW platform, it's probably not going to be Postgres-based. As every vendor has a slightly different flavor of SQL with different behaviors, this will require redesigning your queries, schemas, and most if not all of your stored procedures. Depending on the company and age of the platform, this could be many thousands of hours of work.

Really, vendor lock-in is pretty much a given with data warehousing platforms. Though these days, it's not uncommon for large companies to have multiple DW platforms all pulling data from each other. When one platform falls out of favor, the users just migrate themselves to another since most reporting systems not made by SAP or Oracle are compatible with pretty much everything.