Sooner or later, you're probably going to see many of Google's new products much more heavily integrated with other existing Google products, as well as with each other. Google+ is already integrated with Google properties by the simple fact that it appears in a navigation bar across many of them (although I'm still wondering about its absence from YouTube).
The Gmail team is actively looking to get it integrated with Gmail in new and useful ways. As our CEO Rich Ord pointed out in a Google+ post, Googlers have been heavily emphasizing its potential for businesses.
Expect integration of Google Offers, Google+ and Google Wallet. Words from Google today indicate that they'll all be meeting one another in the future.
Stephanie Tilenius, VP of Google Commerce is quoted as saying at the MobileBeat conference, "One of the things we are going to do with Google Offers and Google Wallet is embed them in our products. So our new Google+ product, we're going to have it there, search and apps. The goal is to…think about Google Maps, with 200 million mobile users. If you're living [in] an area, we're going to find offers. We'll work with all of our Google properties, they will be integrated, but it will take some time to get there."
If Google is looking to dominate so many spaces (search, advertising, offers, social, payments, etc.) it makes a great deal of sense that they tie products to one another in any way that is usable. Google+'s user base is growing rapidly (based on estimates and reports), but those Google accounts in general are numbered way, way higher. Think about every person that uses Google+, Gmail, Google Docs, YouTube, etc. with an account. Any one of these people is a potential user of one of of the other services for the simple fact that they already have an account.
Even if you don't have a Google+ account yet, in some ways you really do. You just don't have the features activated. The account is the Google account. The ID. With Google also providing the gateway to the web for a lot of people (and growing) via Chrome, Android, and Chrome OS, the potential for pushing its services and the simple convenience factor of using them both increase as well.
I think I've said at some point before, that it's almost as if Google itself (for the sake of comparing with Facebook) is the real social network, and all of these different products are just features.