^^
Warsaw isn't any competitor for Moscow, London, Paris or Madrid.
In 1-2 years all comparisons of Warsaw and Moscow skylines will be hilarious. Paris and Frankfurt already are far ahead of Warsaw. Madrid, London and Istanbul also have better skylines and better perspectives. Warsaw can only compete with Rotterdam for 7th place in Europe (continent without any significance in skyscraper construction).
Only barrier is economical. Towers significantly taller than 200 m aren't profitable in Warsaw at the moment.