Originally posted by Rondec Full frame as done by the D700 has pros and cons. On the pro side, you can shoot pretty amazing high iso photos, keeping decent DR up to, say, iso 2000. On the con side, it is only 12 megapixels and so to fill the frame with your eagle, you need a 600 mm lens on a very sturdy tripod, because you can only crop so much. Most birders I know use crop frame cameras, just for "the extra reach."
A lot depends on what your tolerance for noise is. Looking at some of the photos from camera phones these days, iso 6400 on the K7 looks pretty good, but I certainly wouldn't think about trying to sell prints from it.
I think that Pentax will release full frame at the end of next year, as a sequel to the high end APS C camera. It would be nice if they would give some indication of that fact to those who are hanging in there for full frame, for whatever reason, but I doubt it. Hoya has been awfully tight lipped on discussions of future direction.
A D700 with 14-24, 24-70, and a long lens with VR plus an SBxxx super-flash is a serious pro kit. Throw in a fast prime or 2, the necessary tripod, and an APS-C D300 you can now do wildlife with mor res. More reach? Get an excellent Nikon TC.
Nikon fully expects its top shooters to own more than one body.
The issue/decision about FF is not really up to Pentax. It will entirely be determined by Canikon and Sony's pricing for their FF systems relative to APS-C. It's possible that Nikon will do what it usually does with its models, and put out a successor to the D700 (D800 likely), but keep manufacturing the D700 selling it at a lower price point (see note about Nikon getting its crowd to buy multiple bodies).
If the D700 falls to a $1,700 street price, every APS-C/M43 flagship within $500 is going to have a serious problem competing. Canon might do the same with its line; use redundant legacy product sales to drive price points lower. Eventually by doing so Canikon will create a much more cost-effective FF ecosystem leading to the FF domination of the $1,500+ market. This will allow Canikon to scale back their APS-C production and lengthen the advances there, allowing them to put even more capital into FF, driving down the costs even further.
It is perfectly, even preferable, for Pentax to follow here. So long as they are ready. I suspect they are. This is a good time to be cautious, but Pentax's moneyed users and pros who stick it out will very soon need to know if they should stay loyal or jump to another brand.