They cant have liveview with pentaprism, thats the reason why all other manufacturers cant as well.
Either its pentamirror with secondary liveview sensor or using the main sensor.
Sony has overcome it by using SLT, using main sensor to provide liveview while still can use phase detect af.
If you havent use any SLT yet, then you are wrong. The current and upcoming SLTs all use main sensor to provide liveview on 920k resolution screen. It is sharper and clearer than the pictures you get IMO.
And you know why canikons have higher fps and buffer for? Thats becos they dun have a good liveview, so people has to try shoot overhead or under hip using burst mode to try get best possible shots. I have seen many reporters shooting overhead by anyhow guessing the framing and bursting it all the way cos they dun even know what shots they will get. By the way, other than video, i find it useless for canikons to have flipout screen since their liveview is useless.