I'm not a Belgium expert, however I think your yeast are fine (in terms of viability) at that temp, it is not until you go over 100 degrees that you are going to affect your yeasts viability. Higher temps in other yeasts will bring out fusel alcohol and more esters. Belgium beer like it hot and I guess there for don't make fusels at the elevated temps or Belgium beer would be renound for give you head aches. Of course your temps went a little higher so I would be worried accept it was late in the fermentation of your beer.
If your fermentation was slowing then chances are it was all over, by the time your temp was raised. Remember that CO2 and will continue to be released after your fermentation is over so you will see a krausen even after the yeast are just doing their clean up. So your temp raise probably just helped them clean up your beer and the bulk of your fermentation happened at the lower than recommended temps.
So chances are your Saison might be a little quieter than expected but that is for a more experience Belgium yeast user to say.