The Dreamcast is not really an apt comparison. For starters, the Dreamcast had an even shorter lifespan. A considerably shorter lifespan, in fact, the Dreamcast was cancelled only about two years after releasing in the US, and three after releasing in Japan.
As a second point, the Dreamcast was far less proprietary, and far friendlier to indie development after the fact. Most Dreamcast fans are aware about just how negligible the system's copy-protection was. While the Dreamcast used proprietary GD-Rom discs for its games, it had zero protection against burned CDs. And it would boot and play burned CD-R discs without any complaints. So as long as a particular game didn't take up more than 700 MB (and most released games for the system didn't) it was quite easy to download ripped copies, burn them to a disc, and be off to the races. This not only made the Dreamcast a go-to system for pirates, but also extremely popular with emulator developers, and hobbyist game developers. Even today, it is possible for Dreamcast games to be produced and sold, simply by keeping them under 700 MB and releasing them as pressed CDs. If you're not concerned about getting Sega's blessing (and most people aren't) there's really nothing stopping you from developing your own Dreamcast game.
The same will not hold true for the Vita. The Vita carts are far more proprietary. Without Sony's cooperation, it is unlikely that any of them will ever be produced again in the future. Ditto for the game cases, which were of a non-standard size. It will still be possible for the Vita to see digital releases, nothing really stopping that. But even those will have to go through Sony's official on-line store, and they could pull the plug on those as well any time they pleased. I seriously doubt that they will do that. It costs them next to nothing to host those games, and there's always the chance of selling them again down the line through emulation. But I don't think very many developers are going to continue to target the Vita as a release platform.
For physical releases, the Vita is going to have a hard stop, far more so than most other systems. And its relatively short time on the market is going to make it quite desirable for collectors in the coming years. (one could argue that it already has a strong collector following)