Without going on a LBA binge your quickest and easiest path to FF is the FA Limiteds : the 31mm, the 43mm, and the 77mm. Consider the FA 20mm for wide angle and the D FA 100mm macro for telephoto. Beyond that you will need to follow jatrax's lead and go used. I would say that adding a 135mm and 200mm to everything I mentioned would complete you completely.
On the zoom front I would recommend the FA 28-105mm f/3.2, the FA 28-70 f/4, and even the FA 28-200mm f/3.8 if you can find a good copy with a hood.
Other than that, you're just loading up on excess glass.
If/when a Pentax FF comes out there will no doubt be new lenses released or announced for future release.