Hopefully not. The infinite loops are often where a function somewhere returns a value that causes another function to call the first function which returns a value that ..... etc.
Change the value that the function returns, and it fixes it (without changing the save file).
Can't guarantee that other bug fixes won't break the save backwards compatibility though.
savegame incompatibility is mostly only due to the change of the savegame itself. As long as you don't change the read/write methods it's loadable(any wrong value stored because of wrong methods however will be read again)
so if the BUG, is caused because of the code itself crashes, and the wrong values are not stored in a savegame, this won't happen(if the bug appears first in the turn after you have saved) ..if it's accumulating over time, most likely will crash later anyway, even if you fixed the bug itself(this is not so common though)
BUT, considering the number of BUGS reported by people, even if this single bug wouldn't cause savegame incompatibility (bet 99,99% on it that it wont) dozens of other bugs reported by people will cause savegame incompatibility( 99,99% it will not be compatible)
even if you load it properly, and cummulative bug is there already..
any display bug won't interfere with what is saved and what not, but if you have for example double tech rate because of some wonder, even if you fix that, the tech you've gained in the game is stored already, the techs you have discovered due to the bug you have already..
so even if it's loadable and playable, i'd advise you to start a new game, even if you didn't see there was a bug, it doesn't mean it wasn't there!
I wouldnt load a savegame with a new patch, really, so many bugs have been reported..firaxis must fix them asap(and they will, if i would be working there, i'd be working 24h/day right now because there are just too many bugs to be left in) and im sure firaxis will do the same....so just play to get to know the game a little bit, and spare you epic REAL games once a major patch has been released...that's my advise..