The problem is that with Germany going down the rest of Europe including Poland would also be severely weakened.
Why? Poland is going to have markets of Ukraine and Belarus who by the time are bound to be at a period Poland is now, investment opportunities waiting to happen.
Also its not like Germany is just going to fall on its face overnight, the population decrease and the weight of social support takes time, we're talking 50s of the XXI century here.
Whether Poland would be able to take advantage of this situation
Poland does not really have to actively take advantage for at least two decades, just keep growing economically, aquiring a stable and competent elite and investing in its relations with Belarus and Ukraine.
Germany has entered a downward spiral thats absolutely dramatic and long term, even German specialists are divided as to results varying between very bad and catastrophic, Germany is poised to lose a power status for at least a century, possibly permanently.
that I doubt at the moment.
At the moment Poland wouldnt be able to take advantage of an unconscious Jessica Alba in the woods, even doped up on viagra, luckily we have lots and lots of time to sort ourselves out.
Not to mention that without Germany (paying) there would be no EU.
There's a lot of economic and demographical changes that ensure EU is going to fall apart anyway but then again not neccesarily, it might happen that Poland and France take over the financial weight overtime.