SATA2 future proof?

For a new PC with some mass storage I'm considering either:
WD Caviar Black WD2001FASS 2 TB Raid 1 (3GB/s) 209$
WD Caviar Black WD2002FAEX 2 TB Raid 1 (6GB/s) 261$

(Don't argure with the price, I'm from Scandinavia)

They should be about the same speed but the newer standard is way more expensive.
My only concern is wether the SATA2 standard will be phased out, so that SATA2 HHDs will be a problem for motherboards 3-4 years from now?

Nothing is future proof. Almost everything is outdated by the time you buy it.

well at least SATA is backward compatible. SATA 3 is out now and it will work with SATA 2 ports but at a slower speed. but this does not mean that future versions of SATA will be backwards compatible

As stated, all current versions of sata are backward compatible. I don't foresee future sata's not being backward compatible. Normally a new type of connection comes along to obsolete a previous version. So, until something newer than sata comes along, I think you are safe.

There's absolutely no reason to spring for the SATA 6Gb/s drives. Mechanical drives are still very far from saturating SATA 3Gb/s bandwidths. There will be no future technology that changes this.

Inexpensive 8 platter, 25 head drives? Not likely. We are more likely to see large, affordable SSD's first. Moving parts are expensive

Your problem is likely to be finding another SATA 2 RE4 in a few years if one of yours dies.

jdx3ds,
Sure. expansion cards.

mazuren, buy the SATA2 version of the drive. Like Hawkeye said, the drive mechanicals, not the SATA2 interface are the bottleneck.

Something is always better after you purchase it. Buy something that you can afford and fits your need