Incorrect, Haswell H and M series mobile processors all have a max memory spec of 32 GB per Intel.
The current base processor in the Mini is the i5-3210M so the logical Haswell variant is of course the i5-4210M, specs can be seen here:
http://ark.intel.com/products/81012
Likewise the highest end processor in the current Mini is the same as the 2012 15" base MBP processor, the i7-3720QM. Using the current base 15" MBP's processor, a potential high end Mini could have the i7-4750HQ (or corresponding refresh variant) which also has a memory max of 32 GB.
http://ark.intel.com/products/76087
This is all hypothetical of course, but even if Apple were to skimp out with the i7-4700HQ (HD4600 graphics) it would also support 32 GB.
http://ark.intel.com/products/75116
Event the current Mini processors supports 32 GB
http://ark.intel.com/products/64891/Intel-Core-i7-3720QM-Processor-6M-Cache-up-to-3_60-GHz?q=3720qm
http://ark.intel.com/products/65708/Intel-Core-i5-3210M-Processor-3M-Cache-up-to-3_10-GHz-BGA
16 GB SODIMMs haven't been available for a long time and are expensive but I'd be interested to see them tested in the current Mini. It would be seriously pointless for Apple to neuter the memory max below Intel spec, especially when 16 GB SODIMMs weren't even close to available 2 years ago.