Oracle is still a
very good option for data warehousing. When well tuned it's extremely performant and reliable for that purpose. If I were operating an EDW today, I'd choose Oracle over Postgres 10 times out of 10 when it comes to very large scale operations. You'll still see plenty of credible arguments around that Oracle can be optimized to be faster than every major alternative. And you'll still see arguments around replication that are legitimate.
Obviously I don't know what your cost or performance considerations are. If your organization can save a meaningful amount of money and operational headache by switching to Postgres, that can be a big deal for any business. If cost isn't much of a consideration in your operation (that is, what sticking with Oracle is costing you), stick to Oracle for data warehousing over Postgres - at least for now imo.
With Oracle it's the same story it has been for a long time (and probably will remain), it's expensive and a pain in the ass to get up and running the way you want it. Postgres has everything to gain vs Oracle from here forward, it seems very likely to bite into some of Oracle's well guarded high value territory in the coming years.