I wouldn't be in too much of a rush to upgrade if I were you. The PX70 is still a really good set and deals with all the sources you mention really well. Certainly, you might benefit from Full HD with Blu-Ray on a larger set but that would be down to the step up in size as much as any increase in resolution. Personally, I don't think that there's a huge benefit from Full HD from a 9ft viewing distance until you step up to 50".
The PZ800 isn't out until the summer so it's a bit hard to compare it to the Pioneer. The Pioneer is the current king but the new Panasonics aren't far behind and are good value for money. Pioneer won't be launching anymore 42" plasma screens. They will be switching their tech to LCD for screen sizes smaller than 50". They will be launching 32",37" and 46" LCD later this year.
My advice would be to hold on to your PX70 for a bit longer and maybe move your sofa a bit closer when you're watching HD. Wait for the two big hitters to release their complete ranges of new sets, wait for prices to drop a bit (they inevitably will once they've been out for a couple of months) and then have another look around later in the year.