All those multi 100 mhz chip runs much faster than the peripherals, the high speed is just there to crunch numbers.
Re: new parts It's been about a year but "soon" 32MZ DA with display controller should come out. that is going to be interesting. Anyway, page is up and everything. still no datasheet
Also, there is the pic32wk (which is inside microchip's wifi modules) you can find a datasheet but no product page
MK is for industrial stuff (which is great!!) even though i could see myself use one for our automotive modules (4x CAN and a crapton of timers, IC and PWM, which our current dspics of choice lacks)
in this case i am thankful that the core speed is that higher than the peripherals so that everything can be in order before the next operation
Sadly, no high speed (sub ns resolution) pwm like in one of the aforementioned dspic (this is an if-only moment, just like if only the mx had 12 bit adc)
datasheet is there
http://www.microchip.com/design-centers/32-bit/architecture/pic32mk-familyyeah, seems like the peripherals are better,
pic24 : pic32mx = dspic : pic32mz/mk
Keep in mind that these high speed mcus also have caches, which may give unexpected results in first projects.
then i suggest you set up your projects + clock tree with harmony so that you have the startup code ready and then give it the middle finger and access the peripherals directly if you can
this at least is what i'm doing, because i'm not expert enough in pic32 to write my own startup code yet (i've only played with them so far, nothing for work)
unfortunately these new cores are very pricey, i don't know how much it's worth it to use them instead of arm counterparts
though arms with all those peripherals, M4F/M7 core are not being sold for peanuts either