I am sitting here waiting...
I could buy a 5dMk2 but I need to sell my 17-55 f/2.8 IS, as it is an EF-S lens...
my problem is that I can't afford to actually replace that lens!
I am now stuck, as I have started reading rumours.... uh-oh the slippery slope is waiting!
my problem is that my head is telling me, wait until you can afford a complete replacement
(5DMk2 + 17-40L + 50 f/1.4)
but... my head then tells me you know a 5DMk3 could be announced tomorrow and you could end up kicking yourself!
I am now tempted to switch my 17-55 for a 17-40L in preparation and swap my 50 f/1.8 for the f/1.4 USM
but again my head tells me... they might release a lens with the 5D3
Arrrgh, this is killing me! I am turning schizophrenic, next I will be hopping around and talking about "My Preciousssss!"
Like everyone says: buy it if you need it. Money-wise unless something crazy happens that causes tings to skyrocket, the more mileage you can get out of an existing body, the better off you are.
Right now does happen to be a good time to sell the 50mm f1.8; if you were careful about catching a deal/watching the price, you could probably pick up the f1.4 ~$375 -- watch Amazon/Newegg for promos etc.
The only thing you can really do wrong at this point (since you're determined to go FF) is to buy any more EF-S lenses . . .