Is actual version compatible with new frequencies (800/900) ?
Will it be added in the future?
I wouldn’t worry about the sub-GHz bands, which have been around for a while now. Almost no hardware supports them (I’m sure some does, but I’ve never found any).
Well, we just need some extenders to support them 
Do you actually have devices that support only those freqencies?
The extra frequencies are used for signals that are more important, like for fire alarms, water leak alarms and so on.
The standard is pretty old, like 2007 or so, I think, so with the current number of devices that use them I see little need for ZigBee PRO radios.