I was a programmer in the 90s but I didn't become a paid professional until the early 2000s.
I thought that the internet would kill the tabloid press (I am in the UK), and give the public better quality news and information. Instead, the internet became the tabloid.
I thought that it would be the "other guys" who would first leverage the internet as a political platform. People descended from 90s hacktivists, DMT-eating civil libertarians and the like. The rise of internet driven populism was a surprise to me.
I thought that in the future I would own an SGI home computer with superpowered custom chips, or something like a Playstation 2 with an os and keyboard. That is, something highly integrated like the home computers were.
I kind of miss the immersive experience of working with a computer where the whole thing is a unified design and you have a couple of big books which tell you everything you'll need to know to program them, and all the layers of abstraction are accessible and make sense to the programmer-user.
Back then, I thought that the computers of the future would be more profound rather than merely more complex. That they would still be knowable to the lone hacker, only they would demand more from them. Instead we have these huge complexes of ordinary complexity, reminiscent of power station piping diagrams, that we work on in teams as bureaucrats of abstraction. Of course, back then I was a kid, in love with the mystique of computers, there was a lot I romanticized, and a lot I didn't know.
I thought there would be more visual tools for programming, things derived from NeXT Interface Builder, Visual Basic and multimedia authoring systems that people used to use to make CD ROMs and information kiosks in the 90s. And I thought that the development process would be more integrated. We wouldn't be bothering with stacks of batch-mode build tools and things like that, and it would be relatively easy to open a window or play a sound in a high level language without having to do C bindings to third party cross-platform toolkits etc.
I didn't think programming would be replaced with graphical tools, I thought it would be augmented by them, in a unified, ergonomic package.
I thought VR would get going sooner than it did. I was a big fan of Howard Rheingold's 1991 book "Virtual Reality" (a great guide to early VR) and got to try it out in 1993 at a computer exhibition. I used to fantasize about going to VR arcades and playing flight simulators with a bunch of people. Now I do it at home with IL2: Great Battles.
One prediction I got right was shaders on graphics cards. Back in the late 90s I was a user of BMRT, a shareware Renderman-compliant raytracer which introduced me to the idea of programmable shaders. I figured it was only a matter of time before they ended up in consumer hardware, and my ears pricked up when the author of BMRT went to work for Nvidia.