Is promotion from staff scientist to professor possible? (Considering job offer in US) I am a researcher making its way (very slowly) to professor in Europe. After several years of effort and relocations, I have now my own research program and have earned a promotion to supervise PhD students and postdocs. In around three years, I will be applying for full professor positions, hopefully. 

Now, I have recently received an offer from a very famous professor in the US who wants to move in the direction of my research field. It is a permanent position as staff scientist (director) in their group with a close to decent salary. It is clear that with them things will move faster and the impact will be high. 

I am ambitious and still want to lead my own group and succeed as a PI in the future (even if I have certain age now). If I accept this position in the US, will I be still be considered for promotions as professor in the American system? Thank you in advance!
Probably you will not be considered for promotion to professor.  But you could still apply for position of professor, either there or at other institutions.  (It may be considered bad form to start applying for other positions right away; wait a few years.  And by then your "famous professor" may be willing to write a letter of recommendation for you.)