It's highly doubtful that 2 new high resolution formats can be supported in the marketplace. Being audiophile formats, there aren't the many millions of VCR buyers to support both a VHS and a Beta. Even one new audio format on its own is doubtful. Piggybacked on DVD-Video, DVD-Audio has a chance. Most DVD-Audio discs so far include multichannel high resolution (96 x 24) tracks, stereo mixdowns of the 96 x 24, and Dolby Digital (AC3) mixes. (While highly compressed, the AC3 mixes make DVD-A discs backward compatible with all DVD-Video-only players, analagous to dual layer SACD/CD discs being playable in legacy CD players.) As with DVD-Video, DVD-Audio is most likely to be used in home theater type surround systems, so there's another good market fit and reason to buy DVD-Audios: to get more channels and at higher resolution. So far, most SACD releases are stereo only.
Note that I'm not taking any stand about sound here. I refuse to buy a format that has no commercial future. For that matter I also refuse to buy a format that has footprints stomped on the signal in the form of watermarking. Fortunately many of the audiophile labels are not watermarking their DVD-Audios, and watermarking is not required in the DVD-A standards. A brief comment on sound: I think we should withold final sound quality judgement until truly high-end DVD-Audio players appear. It's not too fair to compare second and third generation multi-thousand dollar, high-end SACD players against first or second generation, price-constrained, consumer-grade Japanese DVD-Universal players. And I don't really consider Toshiba or Onkyo to be high-end manufacturers.
Update: A new record label called Hi-Res Music plans to re-release old stereo recordings transferred from the master tape to DVD-A in 96 kHz x 24 bit, but with 96 x 24 bit DVD-Video PCM stereo tracks also included on the same discs. This is an interesting plot twist. Hi-Res does not mention Dolby Digital (AC3) format mixes, which is highly compressed but can support 2 channel sound, so presumably they're skipping them. In audio terms this is good. In marketing terms it could be a blunder. I may happen to have reservations about their approach, but it shows how DVD-A can be used for dedicated audio delivery and it also shows some of the great versatility built into DVD, which actually stands for Digital Versatile Disc, not Digital Video Disc. The full name is actually DVD-ROM, which like CD-ROM is computer-centric, hinting at future convergence issues.
Additional Update: Sony is reportedly releasing combination DVD-Video and SACD players in the $300 range to compete with the DVD-Universal players. That shifts the consumer choice between which high-resolution audio format to get as an add on to DVD-V: SACD or DVD-Audio. I've got to wonder how many hardware makers will choose to build SACD versus DVD-A as that second format. I'd suspect that may be another Beta/VHS type battle, with Sony/Philips on one side and lots of others on the DVD-A side. That's how I see the hardware side.
On the software side, the DVD-A camp is certainly shooting itself in the foot with the watermarking issue, but again, watermarking is optional and not required in the standards. A few hundred SACD titles is great and perhaps double or triple the number of DVD-As out there, but it's hardly an insurmountable lead. Again the DVD-A folks are hurting themselves by not having the standards completely worked out, but at under say 500 total titles SACD and DVD-A combined, it's a little bit premature to say who will win on software availability.
Especially since watermarking is optional, DVD-A is technically superior to 96 x 24 DVD-V (also called DAD). DVD-A adds 192 kHz and a lot of flexibility about mixing, channel use, etc. There is no reason DVD-A cannot sound as good or better than DAD. The technical specs strongly suggest that. In addition MLP gives DVD-A a major practical advantage over DAD (but not over SACD which also has lossless compression), in that it significantly extends playing times with no theoretical loss of audio performance. As long as watermarking is not used, DVD-A is an improvement both sonic and practical over DAD (and I love DADs as a medium).