there are so many variables, i don't think anyone can guarantee you anything. if you want to upgrade, wait until you have some downtime (ie holidays perhaps), just to play it safe...in case you have to troubleshoot anything.
the good news is...developers are updating plugins etc for 10.11. and there are resources (like this forum) to find fixes if need be.
just my thoughts (of course). 8)
Yeah, it's always disconcerting when this type of thing arises. You want to upgrade the OS, (even though this is primarily maintenance fixes)...but eventually, I'm going to have to. Just don't know what AI to go with since I use this for Voice overs only. Have to do some research.