Posted on March 09, 2018 at 17:45Not sure why you'd need to rely on rumors, the documentation, libraries and tools are openly available for review. Your FAE should be able to provide specific advice.
Pin-for-pin compatibility works until it doesn't, ie parts on the market, with data sheets, will be what they are, future products or families might not be, and be inconveniently different while still being touted as 'pin-for-pin'. Do your due diligence. If the Design Manual says make specific accommodations in your design and PCB layout, and power routing, PAY ATTENTION, even if the reasons aren't fully explained, these provide the wiggle room you'll need later to account for differences in future offerings.
I've not had much problems migrating across assorted STM32 parts spanning a decade, I understand how to port software, I understand how to partition my software.
The pin muxing options on new STM32 parts have gotten better, but they don't provide a lot of maneuverability, and frequently choices seem to have been made while being trapped in a conference room with dropping oxygen levels.
Pick parts with more pins, low pin count devices are going to limit your choices (availability, range, pin escape), and options with larger die sizes, advanced parts are more likely to be in packages with 64 to 100 pins.
If you keep expanding the code size are you going to run out of speed to run all of it? Beyond 24 MHz the CM0(+) designs here typically scale very poorly due to inherent slowness of the FLASH and lack of mitigating cache/logic. ie a part running a 48MHz isn't anywhere close to 2x one running at 24MHz
