Skill sets for controls engineer

Hi all,
I am currently working in a medium scale industrial automation based firm. We deal with projects related to process automation. As a newbie to this field, I find there is plenty to learn here.

Now, we use PLCs, HMIs and SCADA for such projects. The program is mostly written using ladder logic or function block diagram (FBD). What I see is that, as we move to complex projects or even in well established automation industries, these languages are not used to a larger extent. Structured text, C language and other higher level programming languages are used.
In my current project, the ABB HMI that is used has JAVA script editing in it. Seriously, JAVA. heck! (Still figuring out how to move ahead in this current project. 😛)
Coming to SCADA software, I feel Visual Basic, MS Excel and MySQL knowledge is of prime importance.

What I would like to know is, which programming language is better to learn or follow, such that I could work with any PLC or HMI and also handle complex projects. I would be trying to get into into well established industries after a year or so. What skill set must I be equipped with? Is it, C langauge, C++, Structured text, Visual Basic, MySQL, JAVA, Python, .net...the list goes on, I guess.

I know ladder is used everywhere, however its still a lower level programming language. I want to learn higher level languages. Where must I start?

Also, please try to share any links, videos or books that needs to be referred. This would be much appreciated.

Thanks,
Sandeep