when will be live in a 64 bit world?

As you mentioned, 64 bit is available now. The LAMP box you're reading this on is 64 bit.

But I don't expect to see dramatic headway until Etch is released officially.

And even then, there's still going to be some stuff that won't be 64 bit.

Quite a bit will rest on hardware vendors. Will those folks using non-free binary drivers be supported with 64 bit binaries? I hardly think so; I haven't seen much movement.

1. This '64 bit' seems to chiefly affect the addressable memory; for example the AMD Opteron still has a 32-bit math processor. This was very disappointing for me because I was hoping for a 64-bit processor like the DEC Alpha. As software gets more bloated (thank you MS VisDuh) machines will need more memory and 64-bit is the only option (actual addressable memory is something like 48-bit - still an enormous number).

2. For whatever reason, these 64-bit machines chew up power - just compare the 'usable battery time' on HP's (Intel) Centrino vs (AMD) Turion laptops.

So, for 64 bits to finally dominate the world we need:
1. a genuine need for more memory - at the moment it is primarily servers and compute-intensive machines which benefit from this.
2. lower power consumption for laptops. This is a big thing - it is very possible we end up with 64-bit on desktops and 32-bit on laptops. Software maintenance will be a nuisance.
3. clearer advantages of 64 bit vs 32 bit - as I said, at the moment it is only memory.

It is clear that AMD has bet on a 64-bit future and no longer manufactures 32-bit processors for general public consumption. Intel however only saw 64-bit for servers (Itanic) but responded to the AMD threat of "cheap server CPUs" by putting out the EMT-64. (Not that AMD is really a threat - they are a tiny company compared to Intel and cannot currently support very large volume production.)

So at the moment I have an Opteron252 as my desktop and a brand new HP with a Core Duo Centrino for my laptop. If anyone asked me about a notebook (given they have a typical life of 2 years) I'd say get a 32-bit. If anyone asked about a desktop - if they run Linux then they have a choice of CPU - if they plan to run VisDuh they may still get away with 32-bit, but who knows which way MS will push the market?

At the moment I'd say it's up to Microsoft to decide when 64-bit is "in". If Intel come up with a low-power 64-bit processor for laptops (or AMD cut a bit off their power consumption) then you have about 2 years before you get really good 64-bit support. (Chiefly because of the dominance of laptops these days.)

BUT - more and more developers with a UNIX history are pushing 64 bits. I've already helped to fix up source code from a few projects so that they are 64-bit compatible. If you code properly from the start then there aren't so many issues to deal with. Also, 32/64-bit issues (and byte order) are chiefly a problem when exchanging data - for example, taking data written on SPARC-Solaris (64 bit Big Endian) and reading on WinDos/Linux x86 (32-bit Little Endian) - or exchanging data via network between these systems. (So a lot of code will run on 32/64 without any modifications.) Software built without data size / byte order in mind are a nightmare to 'fix' - OpenOffice is a very good example of that.

SO - for the most part 32/64 bit is not really a problem, but support in Debian will be a bit flaky until more of the devs have a 64-bit system. Some software is 'broken' and will not function properly when compiled for 64-bit systems - this includes Adobe Inc's software including Acrobat Reader, anything from MacroMedia (do they still use that name?) and the popular OpenOffice. Who knows when people will care to fix these problems.