This is very sound reasoning actually! A Nikon mate of mine has indeed bought his D200 the day before Nikon announced their D300. He called me the same day he bought it, proud and relieved he finally decided on his D70 replacement, telling me he would no longer wait and was impressed by his camera. I told him I heard rumours about a press release from Nikon the day after, but he laughed at this news... Until one day later...
There was Nikon announcing the impressive D300! He wasn't very happy, but I managed to console him by telling him he would have at least three or four months of time enjoying his new D200 before he would have been able to get his hands on a D300...
Even if Pentax annouces sth soon, the same applies... We'll be able to enjoy our present cameras for a while yet before there's actually sth in the stores to makes us want to replace them...
Wim