There is little doubt discussions will be had at PL level about this issue. Teams like Everton, Man utd and others have used the state of the pitch particulalry at Wigan, as an excuse every time they have a below par performance.
What may happen as a result is that they could make a rule that would prevent any further admission to a team that ground shares. This would not immediately affect the current situation but should city or wigan or both go down, they would have to make serious adjustment plans if they ever intended getting back there.
On a more cynical note, should either team manage to stave off the dreaded relegation into undoubted oblivion, the PL and their referees may well ensure its only a stay of execution for the next year = problems solved