The only problem with waiting 6 months is,that in 6 months you are probably better waiting 6 months.It's a never ending cycle and you have to jump on sooner or later.
The reason why they will come down in 6 months is because the ones you are buying will not be the best available and the newer versions will still be at the top of the price range.Just like computers it's a never ending technology fest.
If you stick to either Pioneer or Panasonic you can't go wrong on the plasma side and also the newer Hitachi are getting good writes up as well but are just behind the other 2.
As for LCD,I'm not so clued up so wouldn't want to give advice on them.
For anything over 32" then you are really looking at plasma as these offer the better picture quality than LCD for this size.At 32" or less then you are looking at LCD as plasma is not really available at this size or below.
From what I have seen in the many instances of viewing both LCD and plasma,plasma always seems to me to give that more realistic look to the picture.But,it's your eyes that will be watching it,so inevitably,you'll have to make the decision.
I would also advise to get a proper demo of any sets you are interested in from a dedicated AV shop or from one of the larger stores that have demo rooms.But you must make sure that when demoing,that the sets are being fed with a proper feed,preferably not a shared feed and favourably over component or HDMI,which are the 2 best connection methods.Most shops will allow you to take your own DVD player in and a selection of DVD's to hook upto the sets to see how they compare.