Xen is now on a nine-month release cycle and with Xen 4.2 having come in September of 2012, the next release is planned for the middle of June. Being right around the half-way point for the Xen 4.3 cycle, George Dunlap wrote on the Xen blog about some of the features that are already good to go for this next release.
The features that are finished or are about to be completed include PVH for para-virtualization that takes advantage of some HVM hardware extensions, NUMA affinity support, persistent grants for block devices, support for using upstream QEMU by default, ensuring the ARMv7 hardware platform support is in good shape, ARMv8 (64-bit ARM / AArch64) technology preview support, USB support for HVM guests, a new 16 TiB memory limit, and improvements to the back-end scripts. There's also been work on the libvirt libxl driver, VTPM enhancements, and QXL SPICE support for using the QXL 3D SPICE framework.
These are just some of the features that will be found in Xen 4.3 this summer. Stay tuned for more information and benchmarks as the Xen 4.3 release approaches.