To the extent that AVCHD 2.0 is essentially AVCHD fully progressive i.e. 50 (PAL) or 60 (NTSC) full frames a second, yes X5 certainly handles it. But there is a switch under Settings which has to be ticked to allow editing of this video.
The catch is that when outputting video, while you can select 50/60p, the bitrate provided by Corel still does not go near the new AVCHD 2.0 maximum of 28 Mbps. It remains stuck at 18 Mbps (or in one case, AVCREC, 20 Mbps). That's if you choose Share > Create Video File > AVCHD. However, you can make a Custom template using the Add function which will allow you to use a piece of AVCHD 2.0 video shot with a higher bitrate as the reference point.
While X5, like X4, can also produce 3D video -- the other part of the AVCHD 2.0 standard -- it is anaglyph type 3D, and I for one remain unconvinced as to its validity. However, I don't have either a 3D camcorder, or a 3D player/HDTV , to be able to comment sensibly on this aspect.