It is possible to convert MT4 code into MT5.
It is not possible to convert .ex4 file into... erm... anything. ex4 file is executable, decompilation would be illegal.
It is still possible to ask someone to write a MT5-compatible strategy and write an EA for it. If you have a MT4 strategy or a basic idea you want to turn into an EA. Though result may be unpredictable.
I don't see a reason to decompile anything when you can simply write a new EA for new MT.
Do you mean that MT5 is still in beta?
Yep, is still beta...
Just yesterday they changed some functions and EAs had to be updated...
Terminal in full functionality !
Not a beta, but not accepted by users either. Changes (upgrades) seem to lack a clear roadmap - which does not help in gaining new users