Im upgrading from c2d e8600 building a new system. I have ordered everything but cpu and mobo. Im debating on getting a i5 3750k or i7 3770k with z77 mobo or get the haswell i5 4750k with a h87 mobo. I say h87 because of the 9 series next year that will come with broadwell that is still compatible with haswell. It will have sata express allowing 10GB/s on the z97 chipset with some other upgrades. If I go ivy bridge I would have to upgrade both cpu and mobo or just forget it for a few years until a next upgrade. If I go haswell just a mobo swap.
The thing is that SATA Express won't actually be a huge amount faster in normal workloads - you'll be able to write data faster in sequential, but there's nowhere to get 500+MB/s from anyway, except for video capture. IOPS won't be significantly improved.
I expect you'll find that buying a Z87 MB now is a cheaper option, as you'll need an H87 MB in the meantime, which is another $70+ likely.
Also, SATA Express SSDs will be overpriced I expect, and quite rare until Broadwell is thoroughly entrenched. Especially if the actual SSD isn't backwards-compatible.