I am moving to use a Alpha/Beta ISO and I am wondering will it become stable after official release or will I need a new iso?
The beta ISO image will always be beta, because it contains a snapshot of packages that existed at a particular time, and Ubuntu 13.04 was beta at that time. (It is also beta now, as you know, though it will be released soon.)
Any version of Ubuntu can contain bugs but development versions (alphas and betas) are expected to have more bugs than released, stable versions. It's possible for a bug to cause a problem installing updates. However, except for possible beta bugs getting in the way (which only rarely happens), a system installed from the beta ISO can be updated successfully.
After 13.04 is released, an installed beta version will become the stable version simply by installing updates (in the Software Updater or by running
So, in summary:
If you're going to do new deployments of Ubuntu 13.04 after it is released, it's a good idea to obtain a copy of the stable release ISO for it. (Which doesn't exist yet, of course, but will once 13.04 is "released.")