Oracle will forever dominant HR, Payroll, SCM, Billing, FM etc type systems where more often than not they have custom software on top of it that has been built exclusively for Oracle. There is simply no good reason to switch. If anything the threat to Oracle will come from hosted apps e.g. Salesforce.
But what I've been seeing in our company is MongoDB dominating front end web apps and Datastax/Cassandra for more of the big data, analytics type workloads.
Oracle should be far more concerned with Amazon Web Services.