Via this Oracle.com post, Oracle Solaris will be moving to a continuous delivery model. Rather than working towards Solaris 12 or "disruptive updates", they will be working on smaller, continuous updates to Solaris 11. The post reads in part, "New features and functionality will be delivered in Oracle Solaris through dot releases instead of more disruptive major releases, consistent with trends seen throughout the industry. This addresses customer requirements for an agile and smooth transition path between versions, while providing ongoing innovation with assured investment protection."
Oracle is also extending their Solaris 11 support until at least January 2031 and their Premier/Extended support until January 2034. So it looks like Oracle Solaris 11 will be hanging around for years to come, but they are switching what's left of it to a continuous delivery model. There's also more Solaris demise talk via this OpenIndiana thread.