NetBSD 7.1 RC2 is primarily comprised of fixes since 7.1 RC1, and in particular, security fixes. The raw list of NetBSD 7.1 changes can be found here.
The brief NetBSD 7.1 RC2 announcement can be viewed at NetBSD.org. This will be a significant update to NetBSD 7 but the next major release of this BSD operating system is going to be NetBSD 8.0. There are going to be ARM improvements, a number of fixes, more proper Google Compute Engine support, the Nouveau DDX is now built on NetBSD x86, a lot of new hardware support, and a variety of other package updates and changes for NetBSD 7.1.