If Apple released a new Mini with Skylake and soldered RAM I'd bite the bullet and pay up for a "future proof" amount of RAM (8 probably combined with ssd). Is that the ideal machine no but there comes a point where we have to conceed what we'd really like isn't coming. My 2009 maxhine got an extra lease of life with ram/hdd in 2012 but it can't last forever and unless we get a new Mini I will be one of many forced to chose between a used machine or an iMac
I agree with you about the soldered chip: with a mini it makes little sense to worry about replacing the chip. I would still prefer the RAM be user upgrade able.
I can even be okay with a two-core chip if some discrete graphics were built in to reduce the load on the CPU.