The only thing I can say here is that if you want Apple to do better with the Mini make your voice heard.
That being said I actually expect a Mini upgrade from Apple in 2015. Why? I actually think they had plans to put Broadwell in the machine as that would have nicely improved performance. In 2015 Apple may have both Broadwell and SkyLake to choose from, so the hardware will be there.
As for chips to actually put in the Mini, in 2015, I'd be surprised if there isn't a quad core option however that is more up to Intel than Apple. As it is I think this years Mini gets unfairly knocked by a lot of people in the media. Yes the platform lost the quad cores but it also gained much better GOU performance which is a big advantage for the majority of Mini users. With Broadwell and SkyLake we have the potential to see improvements in both areas of the SoC.
In a nut shell I'm no where as negative with respect to a Mini upgrade as many in these forums. It might be late 2015 but I see great potential here.
I hope your right. I really would like to own a quad core Skylake Mini to replace my 2012.