Yeah, I'm thinking Gollum too. I bet JJP ended up hiring Quinton Kappel for not only Gandalf but also Gollum. The Gandalf impressions in the video below sound extremely close to the ones in the clip JJP just put out.
Based on the few Gandalf call outs JJP included in the clip it sounds like they had Quinton (if that is who they hired) to do a bunch of pinball specific call outs which is only going to make the game even better. Personally I think that the The Hobbit is going to have the best sound, rule and animation design every created for a pinball machine.
As for Smaug yeah definitely a tougher one but check this guys impression out. He sounds fairly spot on. With Smaug being the main toy in The Hobbit you would think that JJP would want to have custom call outs for the toy to increase it's use. If a voice actor for Smaug lines was not hired JJP will be limited to the Smaug lines in the film which really are not many.