Your theory has been industry speculation for a while now. Certainly, what you're saying is possible, but I'm not really sure anybody outside of HP knows exactly how they are going to approach their entry into the market. Their CEO has talked at length about leveraging their existing inkjet technology, which would translate to professional class machines similar to either the Mcor Iris, 3D Systems' x60 line (the old Zcorp stuff), or possibly something like what we see from Objet. These are all high margin, low volume products -- the opposite of the business model you describe.

Another theory is that Stratasys bought MakerBot so a titan like HP couldn't buy them and turn them into the high volume, low margin consumer line you describe.