As you may already know, the first Ubuntu Touch phones are BQ Aquaris E4.5, BQ Aquaris E5 HD and Meizu MX4, but the system is also officially supported on the LG Nexus 4.
Canonical has recently announced that they will support Ubuntu Touch as long as it is technically possible.
This was answered in a Q&A session by Michael Hall and transcribed by thebluedragon, which is an Ubuntu enthusiast:
“Indefinitely, or at least as long as it is technically possible. There is no planned EOL target date. However it is a tiny bit dependent on the manufacturer. They did also say that in terms of updates they definitely plan to handle that better than Android does. They have mentioned that this is possible because the system is now well layered into multiple layers, so they are able to update the base system layer without interfering with the OEM layer,”
Keeping the mobile phones up to date is very good, this way the users being able to receive security fixes. But let’s see if Canonical will manage to make the latest Ubuntu Touch images available for all their devices, like Google does with its Nexus division.