Basic economics
You forgot to mention that it's a time of the cheapest money in the history of the modern world.
As for prices being inflated - if the market is able to bear them, and given that the market didn't crash despite the CHF/PLN exchange rate going the 'wrong' way, I'd suggest that the market was actually pretty stable.
The prices are coming back down. House prices historically raise in value at the rate of inflation. Corrections happen over the same period of time as it took for prices to rise. Regarding CHF/PLN, the first one was a freebie, the interest rates dropped and it made up for the change in exchange rate. Interest rates can't drop anymore...