only takes one shock loss. it's nearly happened a few times in the past 3 years
losing to soderling in FO 2010 was considered a shock loss, even though soderling is/was very good on RG clay, it was still a shock that he lost before the SF in a grand slam
it will end, and i think it will end at either AO or FO
Yes it will end, but not in 2013 i am sure, he is to good for rest of the field, basically at slam you know he won´t loose to anyone outside big 4 and big hitters in form-his last losses at slams besides Rafa or Nole were exactly those 4 guys - Berdych,Tsonga,Delpo,Soderling. Yes few matches were close like Haas RG, Falla or Bennetou at Wimbledon, but he always somehow managed to proove himself. At slams normally first rounds top guys plays vs lower ranked guys, beating them in straight sets and than R3 and R4 you have seeded guys - but most of them are not good to beat Roger on any surface.
BTW that Soderling´s loss was big shock for anyone like Rosol´s match, but honestly it wasn´t such big upset after all. Rosol hitting big and serving big was supposed to be threat for Rafa at fresh grass and Soderling hitting big and serving big should be threat for Roger at slow clay - especially his form back than, loosing in Estoril to Montanes and everything. Those 2 losses are big upsets, but people are making it seems bigget that they were - i remember Roger´s interview - he said those few extra kph on serve and groundstrokes made the difference, that Robin was able to hit through him. He was established top 10 player, runner-up at RG and people still were giving him 0% chance based on H2H... but anyone who saw him vs Rafa hitting big 4 sets without errors knew that if he do it again even Roger won´t stop it.