Though Google hasn't announced anything specific, we're more than halfway through the 18-month rollout schedule the company gave last May. An extra push for Wallet would also fit in with trends in other Google services. Just in the last few weeks Google has added extensive Maps personalization and improved encryption for Gmail. They're incremental changes that are meant to make user experiences better, but they also continue Google's efforts to securely meld all of its services in an attempt to keep users inside the ecosystem for as much of their Internet browsing as possible.
Making Google Wallet easily accessible in Gmail makes it more likely that users will start storing information in their Wallets. For Google, more user data means more targeted advertising means more money. And as Quartz points out, Gmail's user base was at 425 million in June 2012, the last time Google reported a number—that would instantly give Google Wallet a wider reach than other digital financial services have.