Depends on the manufacturer. If they release a full 9.1 receiver, then you'll be able to have height channels AND the standard 7.1 speaker layout. If they release a 7.1 receiver, then two of the surround speaker outputs will have to be used for the height channels, which means the 4 surround channels of 7.1 soundtracks will have to be downmixed to 2 surround channels. I don't know how many output traces the 997's DSP chips has. Can it play, for example, 7.1 in the main zone and 2.0 in the second zone simultaneously? If so, some clever code writing and signal re-routing may allow it to have 9.1 outputs. If not, maybe the 7.1 outputs can allow for two options: 5.1 plus surround-back or 5.1 plus height.

The good news is that PLIIz requires little to no increase in MIPs over PLIIx processing, allowing the new code to fit on current DSP chips. The bad news is that this isn't really Outlaw's decision, since the 997 (like any pre-pro) uses DSP solutions from OEM chip makers. So even if Outlaw is willing to upgrade to add PLIIz, the chip maker first has to come up with the code to do so. What if they decide that rather than flashing their current chipsets, they'd rather introduce PLIIz in their next-gen line of chips? While there was an all-analogue (and all-tube) PLII surround processor from Fosgate, PLIIx and PLIIz have only been implemented in the digital domain. So an outboard box would work, but would need to convert the analogue signal to digital in order to extract the height channels.

BTW, the height info is extracted from the surround channels (discrete or derived), not the front L/C/R channels. So you would input up to 4 surround channels (depending on soundtrack) and the box would output newer versions of those channels (with decorrelated information removed) plus the two height channels.