You are correct, you could buy the Studio now or wait and see if a future Mini will offer a 32 gig RAM configuration or remain at 16 gigs.The Mac Studio seems like overkill for me and I am in theory the kind of user the Mini is made for. I don't really do graphical/video work at all. However, I have an M1 MacBook Air with 16/512 and I've actually been surprisingly unhappy with the memory ceiling. I use large annotated PDFs and have many open at a time, in addition to many Chrome tabs. I find I need to restart more often than I'd like, when memory pressure develops in the Activity Monitor. Since a souped-up Mini is over $1,000, I'm tempted to buy a base Studio, which gives me the 32GB/512 I'd like and then I'd have no worries about future-proofing. But is it just pointless overbuying? Anothe rpossibility is I wait for a new Mini in a few months.
As for me, I loved everything about the M1 Mini except for the RAM limitations. This is the first time I had to switch to another Mac just to get some peace of mind and less frustration. I got the Studio just for the additonal RAM. I opted also to get a larger drive. My results - not so much an issue now about that memory ceiling. The system for me is not any faster/snappier in general use than the Mini. It does do certain application tasks faster. I don't regret my decision to move up. If there was a Mini with 32 or 64 RAM, I would have remained with the Mini. On an aside, I do believe the Mini should be more than capable with 16 gigs of RAM and not having to swap out as much. The lack of memory management with the OS or certain apps is well...a bit ridiculous. I don't see this problem getting better any time soon. This reminds me of Windows years ago where "reboot" was an accepted solution in some instances and killing apps open when they interfered with other apps.