In January Douglas Brown published an interesting step-by-step work around to install a VI 3.5 client on an unsupported 64bit Windows operating system.
In his article Douglas mentions a thread in VMTN Forums where Andre Kemp, Sr. Product Marketing Manager at VMware, provides an interesting answer about the topic:
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We have seen development issues with our new client on a 64-bit host, so due to other priorities the engineers put in the blocking issue to prevent installing the client.
It appears right now the most valid work around is to run a 32-bit VM until we have our 64-bit client available sometime 2nd half next year…
If the above plan is confirmed it’s easy to imagine it as part of a possible launch of a long awaited 64bit Virtual Infrastructure 4.0 with ESX Server 4.0 and VirtualCenter 3.0. Obviously this is a complete speculation at this point.