Some Poles are afraid that Poland will be bought out and nothing will be Polish anymore.
I think it is in the interest of the Polish government as well as investors to maintain integrity so that rights can be protected and laws enforced. But will the Polish government be more interested in protecting the rights of foreign investors or will it be an advocate for ensuring the rights of Polish citizens prevail in any land dealings?
Like the mass privatization in earlier decades of state-owned enterprises, the majority of the population will not see much if any windfall from the sale of Polish land to foreigners.
Investors only part with their money because they expect to get it back with profit.
Agricultural conglomerates may buy up much of the land and then in turn decimate small farmers in the market place.
Other investors may buy up the land to use it for development of housing, shopping centers, theme parks, etc. Such projects may seem to be geared to benefit surrounding populations. However, such structures are not made to last and more often than not have no uniqueness to them. Essentially, they become a form of blight and ruin the characteristic of the landscape which is traditionally much appreciated by hikers, tourists, photographers, historians, etc. Something most agree should be preserved for future generations to enjoy.
There is also the matter of mineral rights. Foreign investors may only want the land to get at what is underneath it. WIth today's mechanization very few local jobs would be created as a result and that's assuming foreign businesses wouldn't be bringing in their own labor from abroad. Again, the results of such extraction may leave behind more scars on the landscape and decades of pollution from disturbing the land which results in disruption and destruction of habitats of indigenous flora and fauna.
Depending on how laws are written Poles may see no financial benefit from outsiders exploiting the land but will be stuck with the cultural and ecological damage.
So another partition would most likely be latent compared to the ethno-political ones of the past.
Another partition may occur due to extreme environmental impacts. A person may or may not believe in "global warming" however no one can deny that climate change is a very real matter here on Earth. We know of the devastations caused by earthquakes, hurricanes and tsunamis. Although Poland may be geologically isolated from these particular threats an increase in frequency and severity of them elsewhere may make regions of the world unlivable and necessitate the mass movements of entire populations. This in turn would create further strains on local environments which could lead to further conflicts as nations fight to protect or claim ever dwindling resources to sustain life.
In the future Mother Nature may do a partitioning of Poland if indeed sea levels rise high enough to significantly or permanently devastate current population centers along the Baltic coast and inland waterways.
And perhaps this won't happen in our lifetime but another ice age event in Earth's climate cycle could very well extend far enough into Poland as it did millennia ago.