There were already standards in the computer industry, its just the big players didn't follow them. Almost all the small-time computer manufacturers, for ex mple, used Zilog Z-80 processors on machines with an S-100 bus and used CP/M as an operating system (this is no guarantee of compatibility, though. Even many "IBM compatibles" in the early days weren't, really).
However, in the US at least, the 'big-time' players, Apple, Atari, Commodore, and Radio Shack, did not follow this.
Also there's no telling what happens when 8-bit machines are eventually replaced with 16/32-bit machines. Without IBM, there's a good chance the Motorola 680x0 becomes the dominant architecture, rather than the Intel 80x86. OTL the 680x0 was used in the Apple Lisa/Macintosh, the Commodore Amiga, the Atari ST, several Cromemco models, and Radio Shack TRS-80 Model 16.
MS-DOS is probably DOA - without IBM, I doubt Microsoft buys out QDOS, which will remain a small-time CP/M work-alike for the 8086. This doesn't mean Microsoft is out of the game; by 1981 they were already selling XENIX, and in OTL 1982-3 they started selling a 680x0 version (this doesn't even mention MSX, Microsoft's standard 8-bit architecture, almost unheard of in the US OTL but big in Japan). UNIX and Unix-like OSes may be more popular in general, especially if AT&T can get its thumb out of its ass and license it at a reasonable price (or sell it themselves at a reasonable price). OTOH, CP/M-86 or CP/M-68k might be the dominant 16-bit OS...
IBM might build another computer instead of the PC. There was some consideration for them buying and rebranding Atari 800s; there were other projects as well, ranging from using an Intel 8085 to an in-house IBM 801 RISC processor. The IBM DisplayWriter word processor is basically a computer, using UCSD p-System as an OS (an option for the PC), 8" floppy disks, and the Intel 8086. Something like it may have been a less successful but stil present "IBM PC".
As for other brands, Radio Shack will likely be the biggest general-purpose computer manufacturer for some time, with Apple and Commodore as their major competitors. Home-market will also see computers like Atari and Sinclair, while the businesses may buy Cromemcos, Kaypros, and other smaller brands instead of a big player.