AMD is likely to ship Athlon 64 processors in small quantities before the scheduled September release, could be as early as August according to Digitimes.
In one hand, support from mobo manufacturers & chipset companies is something we can assume 'done' already, in the other however, the number of 64-bit applications available at the time will be somewhat lacking although the new CPUs are supposed to perform quite well with current software.
According to AMD, it has not changed the launch schedule. However, sources at first-tier motherboard companies such as Asustek Computer and Gigabyte Technology confirmed that AMD disclosed that it will begin supplying two desktop-use Athlon 64 processors, the 3100+ and 3400+, in August. However, given that shipments will reach only a projected 200,000-300,000 units by year-end, board makers expect little impact on Pentium 4-platform products in the short run.