Buy now if you need it now, if you don't then wait. After Haswell is out there will be talk of the next chipset coming out. There is always something new coming up. Haswells main advantage will be power consumption which is more important for MBA and MBPs imo. For desktops the 2012 iMacs have everything you could want for a future proof machine like USB3, Thunderbolt, high end mobile GPU ect ect.