The changes to the MSCE SDK U5 developer shell should be mostly transparent to external and legacy callers; with the exception of dynamically locating and calling the correct Visual Studio (toolset) version's vcvars32.bat to ensure full development access to both respective Bentley and Microsoft development environment, resources, and tools. The primary MicroStation SDK variables continue to be used and though a number of new environment variables exist (SDK*, _SDK*, VS*, VC*) they can be mostly ignored and are initial steps moving towards being able to provide a more common developer shell experience for multiple Bentley SDK related items like; configuration, resource access, and navigation convenience.
For example in a default developer shell you should see the value of SDKVSENV pointing to the correct Visual Studio version (2015 today) vcvars32.bat; which if you have your own custom MDL developer shell may want to or should call vcvars32.bat from that location; from your custom MDL development shell script; that sets the Microsoft Visual Studio (vcvars32.bat) environment variable: WindowsSdkDir.
HTH,
Bob
For example in a default developer shell you should see the value of SDKVSENV pointing to the correct Visual Studio version (2015 today) vcvars32.bat; which if you have your own custom MDL developer shell may want to or should call vcvars32.bat from that location; from your custom MDL development shell script; that sets the Microsoft Visual Studio (vcvars32.bat) environment variable: WindowsSdkDir.
HTH,
Bob