That depends on what car. A couple of cars are going to have major changes for 2013 while others will have little to none. Also depends on how long you keep a car. If you keep a car for just a couple of years you need to buy at the beginning of a model year. If you keep one for a longer period of time then you will get the best deal at the end of a model year.
31 december if car is not yet registered or a rebuild
You still have 6 months to wait and it's june 2013
It might make sense to wait for the next version of Windows to come out, some time in 2012 or 2013.
Depends entirely on what you want. I will say that if the particular vehicle you are interested in is going to be an entirely new model in 2013 then wait. An example is the Ford Fusion which will receive a major revamp in 2013. However if the car you are interested in is basically the same model in 2013 as it was in 2012, you can get a good deal on a 2012 when the 2013 models come out especially if it is a domestic make. You should also consider if you are going to keep the car a long time or trade every year or so. When you buy that new 2012 after the 2013s come out, it is already 1 year old and worth far less in trade in a year or so. May I suggest you look into a Certified Used car from a new car dealer. They are low mileage, excellent vehicles that sometimes even have a better warranty than a new car. You can save a bundle on a Certified Used car.
The current Nexus 10 is has some pretty robust specs, so you can't go wrong with it if you purchase it now. If you're willing to wait however, the second generation Nexus 10 is due to come out in the 4th quarter of 2013. Latest rumor on it is that it will be developed by Asus, who has developed both the 2012 and 2013 Nexus 7.
wait till Q1 in 2013....
No, becaue you will not beable to have time for them to be delivered and store may be empty by then.
wait for ngp to come in market
If you want to buy a stock immediately, you should buy at the ask price. If you are willing to wait for a better price, you can place a bid lower than the ask price and wait for a seller to accept it.
You should wait for holiday sales, you can find way better deals.
about a year or two
Wait! 5 will be awesome and 4 is...a 4.