Silver Castle will be the next Williams, but on a lower scale.

Stern will be plagued with more and more quality issues caused by outsourcing like all greedy American Company's and the resale of there products will plummet, and hence there sales will drop to the point where they are no longer a major player. While this happens they will do a dead cat bounce but it won't survive.

Top condition Williams/Bally DMD games will continue to hold and increase in value slightly above inflation.

More and more Pinball Machines will fall into NON Pinball Players collectors hands, and be locked away.

Non Commercial themed Pinball Machines with become more and more sought after. Machines like Mettalica, ACDC, Ghost Busters will all be seen as rubbish Games in 10 years time.
Take a look at most of the Popular Titles MM, CV, TOTAN, WH20, MB, TOM, SS, FH, CC, WW, FT, RS They came from the heart, not from some shitty Movie or Rock Band or Car. They will be regarded as TRUE CLASSICS. It has to be unique to become collectible!!!!!
Sure you have great machines like IJ, STTNG, TAM, TZ etc but they are a minority.

Machines will become more complex and more expensive and lower volumes.

Basically the Dutch and Germans will take pinball to the level it needs to be and the American made Pinball Machine will be no more.

If it was up to Stern you would have no Hi FI sound, no Color HD displays, no 3d Translites. Just the same old shit with the only changes made to reduce production costs, and increase spare parts sales.