In spite of that I believe Warsaw will lost its lo-co connections soon
I'm puzzled as to why you think Warsaw will lose its low-cost carriers (or at least until Modlin opens). Big city, lots of people, some money floating around. The centre of Warsaw is attractive so has inbound tourism as well.
Maybe a few of the more marginal routes might disappear, but with LOT having significant issues of its own, SkyEurope having quit WAW and the demise of Centralwings, it seems to be easy-ish money for the remaining stronger LCCs. Wizz might be making a lot of O'Leary-esque noise, but in 2009 would they really pull out of one of their main airports and give a monopoly to Norwegian ?