I use SwiftKey too, and am quite happy with it. Nonetheless, 'm not really convinced when it comes to enhancing a keyboard with such a feature without first having tweaked it to near perfection. At the moment, I still get quite a lot of autocorrection errors that I need to then fix manually (if I happen to notice them before hitting send..), which is not as quick as it could be, but still bearable. I can't imagine going back and trying to fix something if whole sentences are typed in one go. Having said that, if I didn't have to worry about autocorrection errors, this would be awesome.

One of the reasons why SwiftKey doesn't perform as well as it could for me might be that I use it with two languages, typing in each more or less 50% of the time. The fact that it can predict the next word based on the current one does help here in order to get the language right, but the three measly slots it has for word suggestions are still cluttered with words from the other language most of the time when I type. I think performance would boost if it could detect the language during the first few words and only suggest words in that language from that point forward. Then again, I often mix the two languages in a single sentence..