Microsoft announced various new features in SQL Server 2016 CTP2 release. One of the important features is related to Trace Flag 4199. This is the trace flag that was provided to combine various Query Optimizer related trace flags under a single trace flag. That means rather than enabling those multiple trace flags you can enable this single trace flag to overcome various Query Optimizer related issues. Trace flag 4199 covers various trace flags those comes under 41xx series.
In SQL Server 2016 CTP2, there is no need to enable this trace flag because in this version the behavior of trace flag 4199 has been enabled by default. The behavior of this Trace flag has been combined with compatibility level 130. If you are using Compatibility level 130 then all the optimizer related hot-fixes released till SQL Server 2016 RTM will be enabled by default without trace flag 4199.
Keep in mind that this behavior will not be applicable for the Optimizer related hotfixes released after SQL Server 2016 RTM version.
For more information about this trace flag you can click here.
Prince Kumar Rastogi