I don't know, but I'd suspect that it is not possible to retro fit the PIP into existing engines.
It's possible to retrofit the PIP, but it would be hugely expensive - most of the HP Compressor and LP turbine is new. Once we're over the hump of certifying the PIP, I suspect GE will look at a 'PIP Light', where they retrofit the easier PIP upgrades into the baseline engine. There are already over 200 engines in-service so there will be demand to be able to upgrade those.
I noted before it's hard to do apples to apples comparisons of 'seating' because there is no such thing as a 'typical' seating layout. The bottom line is that the 747-8I still has quite a bit more 'floor space' relative to the 777-300ER and even the -9X. They also did something rather cool with the Intercontinental upper deck - aft of the 'hump', they cleared out the main deck attic space and provisioned for sleeping quarters. Some of the VIP customers have taken advantage of that to install some ritzy bedroom setups. So far I don't think any of the regular airline operators have elected to take advantage of that, but it would be relatively easy to do - the upper deck is typically business or first class anyway - wouldn't it be nice - on a 12 or 14 hour flight - after reaching cruise to head to your private bedroom in the back?
