I am thinking about buying a Mac pro to use it for video , but i have been told that new Mac pros are coming out...
The Sandy Bridge Xeon's aren't out yet (due Q3/Q4, depending on the model). And it will take additional time to get a system shipping. So it's extremely unlikely they'll have it out this year. I'd figure on March - May of 2012 realistically.
Update with Thunderbolt?
Does not make sense to have the Pro machines without this feature.
It's not necessary for workstations, as you can get much better bandwidth via other card tech on PCIe slots (think RAID cards with a sufficient number of disks for disk throughput).
Where it could be useful, are those that also have laptops they use for location work, such as video recording (just attach the TB storage device to the workstation, and start editing for example).
Now the X79 chipset that will be used in the next MP's doesn't include TB at all, so the only possible way to get it, is if they opt to add in a TB chip.
But Intel's strategy seems to be that they want both data and video information over the port, so there would need to be a way to attach a DisplayPort output from a graphics card to the mainboard in order to connect it to the TB signal. So far, there's been no public information on this (technically possible).
Ultimately, it's possible, but not a guarantee it would make it in the next MP if they wanted to (and a TB chip adds cost, which Apple isn't keen on - look at other port tech user's have asked for over the years, and still not gotten).
While the X79 preliminary list of supported features is nice and Sandy Bridge is also nice, sadly
The X79 doesn't provide TB support anyway (it does combine the usual separate chipset and ICHxR into a single part though).