This could be devcisive. If the push through Belgium can begin with a German thrust south from Dutch territory instead of a thrust West from Germany proper, it would save a lot of time that was used to advance on a narrow front. If the German forces can take all of Belgium, it would pave the way for an advance on Dunkirk, which would keep the Entente from flanking the German Forces as happened in OTL.
There are two things to take into consideration:
1) If the Germans can use this advantage to take Paris in the opening campaign, then France is done. Peace with the Western Entente would indeed come "before the leaves fall off the trees", as Wilhelm II put it.
2) If the Germans are halted before advancing on Paris, then they are in a much better position, meaning that they will keep most of their gains in Northern France, including access to the Channel. The Pale of Calais would be useful to disrupt at least some traffic on the Channel, which could hinder logistics for the BEF. If things go similar to OTL from this point in the East, then it is likely that the final German offensive in the West could take Paris, simply due to the smaller distance that would need to be traversed by the German Army.