New 2.0 version available:
http://forum.corecodec.com/viewtopic.php?f=3&t=3241

some changes:
- CHG: Updated IDCT to support ARM NEON Cortex A8 Support
- CHG: Updated Blitter YUV/RGB for ARM NEON Cortex A8 Support
- OEM: Initial ARM NEON Cortex A8 Support (iPhone, Touch, Linux, Windows Mobile)
- OEM: SDK NVIDIA CUDA 2.3 support
- OEM: Removed the windows direct3d requirement for CUDA (it can now be native)
- OEM: Updated GStreamer plug-in

As changes are for OEM, is Nokia using Corecodec in N900 in coming firmwares?

As the source in question appears to be closed, the answer to that is almost certainly no. You could try asking the Corecodec people if they will release a version of Coreplayer for the N900 though.