sata2 allows for higher bandwidth, and ncq. To me, it sounds like sata2 for now is a gimmick, because even in the older sata, and even pata, no drive could utilise the full bandwidth, and drive mechanics are governed by physics. Take a look at wd raptor, which spins at 10K rpm, and that is at the sata1 specs. Either drives get faster, which is mechanically very challenging to remain precise, or the platters get denser. Dense platters, mean that more data can be transferred at the same rpm. Ncq, is another story, seagate sata1 drives have been utilising this in quite a number of there drives, and providing you have support in the mobo chipset then you can take advantage.
So to answer the question, sata2 is something that should last theoretically for quite a few years (that is my opinion) until solid state devices or some other more efficient way to store data, but i wouldn't bother with it.
ECS L7VTA mobo
2 x 512MB DDR400 Geil Value Ram (w/blue hs)
NVidia GeForce4 MX 420
Seagate Barracuda 120GB, 7200Rpm, 8MB buffer (pata),
Seagate Barracuda 160GB, 7200Rpm, 8MB buffer (sata-ncq)
BTC1108IM dvd writer (8X)
Aopen 1648 dvd-rom
sunbeam fanbus controller
Philips 190X5 19\'\' LCD monitor 12ms