Also, if the allies abandoned Poland like they did Czechoslovakia, what were Hitlers plans after that? Annexing Alsace-Lorraine? The German speaking part of Belgium?
Establishing "near colonies" in eastern Poland to feed Germany, longer term - invading USSR and doing the same there.
According to "Bloodlands" by Timothy Snyder the plans were to get rid of most of the Slavic populations by starving them, keep the rest as uneducated slave labour. More http://en.wikipedia.org/wiki/Generalplan_Ost http://en.wikipedia.org/wiki/Hunger_Plan
This was tried in eastern Poland in Zamość region, but the people there revolted and kind-of won http://en.wikipedia.org/wiki/Zamo%C5%9B%C4%87_Uprising
It was also implemented in various regions of USSR conquered in 1941 and later.
Of course once Germany had the teritory of Austria, Czechoslovakia, Poland, USSR, and easy access to Romania oil - it could do what it wanted with the rest of Europe, so I doubt it would save western europe from war in the long term.