Steve Langasek has brought the topic back up in the ubuntu-devel mailing list, after it was almost entirely ignored after the UDS session. <!--more-->
As per <a href=" https://blueprints.launchpad.net/ubuntu/+spec/foundations-p-64bit-by-default">the Launchpad blueprint</a>:
<blockquote>It's expected this cycle that Multiarch will provide superior 32-bit compatibility for any packages that previously required ia32-libs, as well as a scalable way to add compatibility for other libraries going forward, removing one of the main pain points for running 64-bit by default. Adobe has just released a supported 64-bit version of flashplugin, removing one of the main causes for users to need 32-bit compatibility on Linux anyway.
At the same time, the availability of UEFI only on our 64-bit images gives another compelling argument for running 64-bit instead of 32-bit, offering features like a fast UEFI boot instead of a slow BIOS POST and possibly secure boot capabilities (or possibly, the need to use UEFI to be bootable at all on certain secureboot-enabled hardware).
Should we switch to promoting 64-bit ISOs by default for 12.04 (on the website, in pressings, etc)? What other blockers remain? </blockquote>
In <a href="https://lists.ubuntu.com/archives/ubuntu-devel/2012-April/035054.html">the post to the mailing list</a>, he said the following:
<blockquote>Note that we're talking about three changes here:
Right now, the only "major" blocker that has come up in the discussions is that not all netbooks support 64 bit - and before you go and wave that away with the argument "They are all old and ancient netbooks anyway", its not true - there were a few Intel Atom CPUs made in Q2'11 that don't support 64 bit.
Other arguments include the memory overhead of 64-bit:
I have to agree - I decided <em>against</em> installing 64 bit on my ThinkPad, since I only have 2GB of RAM in this machine.
Also mentioned is that regardless of which Ubuntu decides to use as the default, both the 64 and 32 bit versions (amd64 and i386) will be available for download and will be supported for the duration of 12.04 LTS - which is 5 years. As such, those who install 32 bit don't have to worry.
There is currently no word on how this would affect Lubuntu, Xubuntu and Kubuntu, although the only ones that might be negatively impacted by a possible change would be Lubuntu, since Lubuntu is designed to be installable on older machines that might not support 64 bit.
Download the official 2buntu app for both Android and Ubuntu Touch.