Future proof ? Knowing technology today, it'd probably a suitable platform 5 years down the line. It is afterall a workstation ideal platform.
Not so sure about i5 being a watered down i7, if it is the case, it goes against the convention of Intel mobos previously. Previously an x38/x48 would hit the market at a cost, then the p35/p45 would come along with lessons learnt plus the newer version of the i/o chipset. That much cheaper.
Saying this now, I'm not sure if the new i5 mobos are going to come with SATA3 (possibly) and/or USB3 (less likely) as standard.
And ofc ASUS/Gigabyte will produce another 5 versions of the mobo.