Kerber? She has a "chance", if you mean win a set. So yes she could win a set. But if their respective forms hold, no way she's going to be able to take two full sets from Maria. Maria is too strong at the moment.
Maria could be stopped in the Quarters by Bouchard (if she beats Cornet, if Cornet wins, Sharapova has a ticket to the semis) where she could face Lisicki or Ana. If it's Lisicki then Maria is losing, if it's Ana I'd say it's 50-50
Of course she could also face Halep in the semis (I don't think she'll beat Lisicki on grass but if Ana wins and Halep faces Ana in the Quarters Halep can get through) and it'll be 60-40 in favor of Halep.
If it's the finals the only person who can stop her then is Petra, and she'll have to tree like she did against Venus. Otherwise Sharapova could be looking at her own "Serena Slam"
. I don't wanna post them but you may see them again when Serena snatches Maria 
I hope this doesn't give her bad luck. My faves always flopping when I watch them on TV. 
They should just **** already. 
but not you underestimating Ana like that 
*bookmarks*
and Marat was so damn hot 