If this was ever to happen, it would need to have been started months ago. Pinball collectors are more than happy to pay huge amounts of money to "start up" companies without a track record. Place the WMS name up in lights again, and pinheads would not go to the boutique manufacturers. It is that simple. In my eyes, Homepin will eventually fill that void, as JJP can't.
Stern will be around for a long time and will most likely be producing pins for many years to come - as long as they understand their market is now the home collector - so they need to be a bit more realistic with their pricing.
From a logistical and practical point of view, the only way WMS can ever get off the ground is for the profits from the gambling games etc be pumped into the new pinball venture. That will never happen.
I think the MM remake ideas are filling that void. Williams are kinda already there.