Hope you don't still feel the same way because I can personally assure you that the last thing Hornacek will be receiving is an extension after the magnificent job he's done this season.
I haven't researched this, wouldn't know where to start - but I wonder how often a true lame duck coach (as opposed to one that's just going through tough negotiations) ever does a good job? It's hard enough to get all the players on the same page, doing it in the final year of your contract has to be close to a kiss of death.
As for whether I still believe they've outperformed expectations, yes, but only up to the start of this season. This team has more talent than it's showing on the court and that has to be laid at the feet of the coach even if he is a lame duck. We had more talent than we showed last season too but there were extenuating circumstances for the disappointing results. There really aren't many excuses for this season.
I'm still generally satisfied with what McD has done. We had embarrassingly few assets when he took over, now we're middle of the pack (in assets). At some point though those acquired pieces need to fit together. If the next head coach also fails to assemble them into a cohesive unit, you'd have to point fingers in Ryan's direction.