Well, what we know is:
1. Stern has the rights to do a Godzilla theme pinball game of some kind.
2. Gomez has stated that they only do a theme if one of their team really has its heart and soul into working with that theme.
3. Dwight Sullivan stated on a podcast (I think) that multiple teams at Stern really wanted to do a Godzilla themed game.
This really seems to imply that a Godzilla game is coming sometime, but as far as I know everything else is up in the air. Now the puzzle pieces initially made me think that Godzilla was a ways off because it was too obvious with the scales and then the Japanese writing. Now I'm thinking there's a possibility this is a more elaborate troll. Get everyone thinking it's Godzilla, then throw them off the scent with the puzzle, then release Godzilla in two weeks. Sort of a big reach here though.
Honestly I don't blame Stern for keeping things close to the vest. Things get really out of hand when a theme is known before the reveal. We get everyone designing the ultimate pin based on the theme and there's no way the actual pinball machine will live up to this hype and everyone is disappointed at the reveal. I kind of like the secrecy as well as it's a lot of fun trying to guess what's next. After the reveal I'm either not interested or bummed that there's another cool game out there that I probably can't afford to buy.