Presumably market forces dictate that its only a temporary thing anyway, until Poland is brought more into line with the rest of the EU.
Once plumbers start getting scarce in Poland, they will have to pay someone more to get that washer fixed. Another assumption, but I presume a Pole would prefer to live in Poland rather than have to move over here to get a decent wage, so they will move back once the decent wages come available.
In fact, the best thing to do is go and move to Poland whilst the property price is still low and then cash in once the boom occurs.