It will eventually be 870 feet tall 50 story indeed, around 670 feet tall to the roof saying how tall the syringe at the top is.
Renders of the latest version from defense-92.fr :
This model seems to feature the thing as it is currently as well :
Rumour from french site PSS has it that construction might start in april at last. For now they're still working on a few preliminary things, a car parking in particular but the low-rise that the tower will replace is not torn down yet. You can see what's going on
over here.