Will it be possible to create apps/games in Java SE or Java ME on new Ubuntu phones?
Yes, For example, the JogAmp JOGL Jake2 port is known to run on Ubuntu Nexus 7 touch tablet using IcedTea and OpenJDK.
You have access to all Ubuntu java packages that you normally find on desktop.
OpenJDK implements a JavaSE like environment.
You can access OpenGL ES 1 or 2 directly from Java using the JogAmp library for most flexibility, especially suited if you write your own engine. The JogAmp JOGL implementation is provided by the libjogl2-java package.
You may also use existing java game engine library’s such as libgdx, playn and jmonkeyengine that will get you up to speed if you want to create a game from scratch.
You could write Java applications the same way you would write them for any linux distro.
Assuming you are on an ARM device you will also need to install a JRE compatible with ARM devices, to run your application you would do it the same way as a normal linux distro (because it is a normal distro),
Basically, it's not worth it, yet.
Summary: Ubuntu Touch has an Ubuntu core, and is a linux distro. You can write Java apps for linux distros, so yeah, you can.