AT&T continues to claim it will offer tethering support to iPhone users on its network - but remains completely non-committal when it comes to offering any concrete date for introduction of the same.It has been a year since the carrier promised tethering would be enabled for US iPhone users, “soon”, but speaking to Computerworld an AT&T rep could only say, “We plan to offer tethering on the iPhone but have not announced a date.”Nice. Particularly when you consider AT&T Mobility President Ralph De La Vega promised tethering would come “soon” way back in November 6, 2008.We do know AT&T has found it had to upgrade its network to support this feature, or so it claims. Some analysts suggest the com