How reliable does the E-M5, E-PL5 or GH3 focus for weddings ?

I am just thinking about when to switch to m43 from Oly-E-520 type cameras.

I know that modern Microfourthirds camera focus quite fast, but

( a ) weddings are often quite low light ( usually not extreme low light, or, in the seldom cases of extreme lowlight you can take a few seconds for focussing ) but usually medium low light and

( b ) its not so that "targets" are always moving to the camera or away from the camera, i dont need Continuous-AF, but alltogether there is at least some action, the people are doing something or might be speakig something and the photographer might be able to hold the cam still during taking the shot but perhaps not perfect still during focussing - and Contrast-Detect-AF might be not always easy for the camera in such situations ? or am i wrong ?

I dont do weddings often, but sometimes, my camera should at least be able to photograph a wedding, and E-520 type cameras do also not focus perfect, but at least have the option for phase detect AF what microfourthirds cameras do not have. On the other hand i heard positive things about m43 focussing since the E-P3 ff

--
cheers
Mr.NoFlash