I want to buy a MacBook Pro with an i7 processor, does anyone know if there will be an even faster processor offered in the near future? Seems like the i7 has been out for a while....
As others have pointed out, Intel simply uses i3, i5, i7, to categorize processors within a particular generation. What you're looking for is the processor microarchitecture (e.g. Sandy Bridge, Ivy Bridge, Haswell).
The i7 processors in the current 15" MacBook Pros are Haswell, and Intel has since released Broadwell, as well as Skylake.
Apple refreshed the 15" MacBook Pros just a couple weeks before Broadwell was released (i.e. they skipped Broadwell altogether).
Intel then released Skylake at the beginning of this year (so the 15" MacBook Pro is essentially 2 generations behind).
You have to remember, Apple doesn't have much competition as far as OS X is concerned. If you want / need OS X, you essentially take whatever Apple gives you (you can go the hackintosh route as well, but that's niche enough that it really doesn't affect Apple in an appreciable way).
This means Apple feels very little (if any) pressure to keep pace with technology / hardware / other computer offerings, so updates are driven primarily by profit. Most people see "2.6GHz i7" here, and "2.6GHz i7" there, and conclude that they're the same thing. They haven't the slightest clue regarding different microarchitectures / IPC gains, and the lack of competition makes it all too easy for Apple to exploit this consumer ignorance.
Point being, if you sit around waiting for an update / refresh, you might be waiting awhile. Updates won't be predictable as they are with Dell, HP, Lenovo, etc. (where they update the hardware as soon as they can get their hands on it). The further Apple hardware lags behind, the greater their profit margins (so as long as people are buying their computers, they're in no rush to update them).
This is why I always encourage people to buy last year's model (as opposed to the "latest and greatest"). They're significantly cheaper, you can still find them brand new, and the difference in performance ranges from negligible, to literally nonexistent (e.g. the current MBP uses the EXACT same processor, integrated graphics, memory, as the previous generation).
So, while Apple's hardware hubris is certainly a bit frustrating, they're to a certain extent shooting themselves in the foot with the more knowledgeable consumers. As they continue, a greater and greater portion of their customer base will catch on / wait for an update only to purchase the (almost indistinguishable) previous generation at a discount.