Hi grelhado,
While I have not been playing as long as you, I may have a couple suggestions that could help.
As far as rythem goes, start to count the beats not only while playing, but also in general activities throughout the day.
For example, if your in the car and listening to classical, country, pop, rap whatever type of music. Start to count and tap along with the rythem. Once you have that down, start adding beats inside of beats, changing them up to break beats for instance.
Also, think about it more. If your making a peanut butter & jelly sandwhich for instance, count beats while your doing it. I know, and odd example. Just trying to get across that a great way to get better at something is including the practice / activity in your everyday, day to day things. After awhile, it will just become second nature, although people may start to look at you weird wondering why your whispering to yourself

As far as technique goes, just practice slow. Try to stay away from bad habits that im sure your teacher tells you about. It will mature over time, and eventually when your in the middle of a piece you wont need to be thinking about it anymore, it will just happen naturally.
I had a hard time slowing down, but when I suffer from a problem that is due to technique, slowing down always fixes it!
As far as a concert pianists, I personally think the only person that can say you could be, or could not be is yourself. Just depends on how much you really want it. The more you want it, the harder you work, the harder you work at it the more of a chance of it happening.
Oh yea,
Another good idea for rythem. Start playing with other people. Like ask you teacher to do some 4 hand piano with you. This will help force you to keep rythem. There is also the metronome as well, but personally I despise it:)
Hope some of these ideas help.