Better them than us.
Mark my words right now - any team who offers Al Horford upwards of $25m+ a year for the next 4+ years is going to regret it in a huge way.
I personally think he will be a good signing for at least three of those four years. Over the last four years his stats have been pretty consistent in just about every category, advanced stats or not, with the exception of his rebounding, which has trailed off some as Atlanta has played him more on the perimeter, and his three point shooting, which he has developed into a weapon just this year.
I think Horford's game will stay consistent for a few years but probably not be great at 34 years old. But he will give great value for that contract under the new salary structure for at least three years, IMO.