Standards for DOCSIS 3 have been released. It now has a maximum downstream rate of 160Mbs (up from 40Mbs) and upstream of 120Mbs (up from 30Mbs). Those are in bits. In bytes, those are speeds up to 20MB down and 15MB up. (Something seems odd, as I think the current downstream actually goes to 12 or 16MB down, or 96-128Mb?)
You're getting bits and bytes confused. Just about every telecom spec I've ever seen refers to bits/s, not bytes. Also, the speeds refered are typically the "wire speed," so typically your throughput will not be the same as what is advertised (due to things like frame headers and checksums).
The big advantage of DOCSIS 3 is channel bonding (that will allow for much more bandwidth. This is good for the cable operator, so that they can get more modems on a port, not necessarly to increase speeds to the home. That is still a good thing for consumers, because theoretically the operator won't have to segment nodes to maintain throughput, keeping upgrade costs low.
However, since there are no DOCSIS 3 modems or related equipement yet, this will cause a big hassle since everyone will need to upgrade hardware (this is a complex change to a specification and a firmware upgrade isn't possible). Comcast, for example, still uses DOCSIS 1.1 modems because they have a huge installed userbase that they would have to deal with. In other words, don't hold your breath, and don't expect a wholesale change.