It can run windows 3.1...all the multitasking you want.
It's extremely hard to do multitasking on a single console anyway, that's why MP/M was a multiUSER and not a multiTASKING os.
Yeah, my kids keep complaining about my jokes, too...
And while it was very late for April 1st, it wasn't at all serious, but a way to reminisce that there were days when DOS indeed was both "the hottest stuff around" in PCs and even had a future in terms of feature expansion. This was all well before even the 80286, let alone the 80386!
And yeah, there was MP/M, a multi-tasking and multi-user version of CP/M, which was in use before the IBM-PC even launched: plenty of S-100 systems out there used it to support businesses too big for a single microcomputer yet too small for a mid-range system.
I know it's hard to believe these days, but there was a lot of multi-user and multi-tasking going on with RAM sizes of 32-128K and certainly 640K would have been regarded as outrageous in an MP/M setup, most PDP-11 (mid-range) ran with less.
Microsoft
did produce a multi-tasking DOS prototype with an internal version number of DOS 2.5. Somehow the company I was working at at the time had documentation, which I was given to read, but I don't think we ever had code for testing and it never left beta, instead the main focus of the next DOS release (3.0) became HDD support and the hierarchical file system (inspired by Xenix).
Digital Research also continued to make multi-user derivatives of their DR-DOS, mostly for embedded use and with GEM UIs, which I was also using for some of my projects back then, long before Windows ever became remotely usable..