Should I wait for 3D processor or buy new i7-990x

I don't know about compatibility, but if you're upgrading you should definitely go Sandy Bridge over a 990. Why would you spend a thousand dollars on a processor? For that price, you could get a 2500K and a motherboard to match, with a beastly graphics card (or two) into the bargain!
Sandy Bridge CPUs are roughly as good as the 990 when you overclock, and cost $750 less.

What mobo do you have?
And if you do buy the lga1155 you would instantly have compatibility with the newer 3d transistors.

You can get a 990X now.

You'll have to wait until early 2012 for Ivy Bridge.

Maybe October or so of this year, Sandy Bridge "E" will be released. That will be faster than Ivy Bridge and the current Sandy Bridge, but requires a different mainboard.

Then of course there's AMD's Bulldozer, coming in June or thereabouts.

You'll have a lot of choices if you decide to wait.

Wait for a month or so for the Bulldozer, if the leaked specs are correct, an 8-core BD should be equal to the 990x and should be much cheaper. You will need a $100 motherboard and probably new RAM if you don't use DDR3 now.

1-if by 3d u mean ivybridge then you will have to wait quite a while they will be out early next year
2-dont buy 990 as it is extremely expensive and the 2600k performs almost as well at 1/3rd the price. 990 has a really performance to price ratio in comparison
3-if you really want to buy intel's enthusiast class processors then wait a few months sandy bridge e will be out then at least you will get value for money