I need to open by saying that this is not a guarantee of the actual demise of a product, rather my view on why it is obsolete. I have a feeling that the mobile workstation will be around for a while longer, but likely with a few small changes.
What is a Mobile Workstation?
In a nutshell, it's a "laptop" which is packed with the power of an entire data centre, all in the compact weight of a elephent. Serously, they are powerful machines, but weigh a lot (mine is over 3.2Kg). They look rugged, but aren't exactly practical for carrying around. They look like the user has a clue what they are doing. Why else would they be lugging round a behomoth like that?
Who uses them?
I have one with work. It is robust, and has roughly enough resource to run what I need to most days. It's always worrying to say "most days", especially when it already has 32GB RAM. Something I regularly use 98+% of. I requested something with this level of power as I knew I needed to support a produciton system whilst on the go, and need to run the database locally. Something which uses around 20GB RAM when it's running.
It doesn't run often. I'm working on a new project which has a lot of different components. In the production environment these run on different servers, so I run them all on different virtual machines. I've written about the reasons for using virtual machines in development previously. Those virtual machines take a lot of resource to run. There's more efficient ways of doing so, and many reasons to avoid using virtual machines in development. Regardless of how it's set up, it was needed for the power.
I use a workstations because I have never used a Mac. When I started my current role, I knew I needed something with a lot of power. A lot of jobs I was interviewing for were giving new developers Macbooks. They can come with some serious resource in a fairly pleasing case. All the power, some good looks, and not a lot of weight. Factor in Apple's reputation for build quality, and the cost of them doesn't seem too bad. When you compare the cost of a Macbook against a Dell, it's not actually a crazy proposition.
Why are Mobile Workstations dead?
Quite simply, there's no need for them. They ar expensive pieces of equipment because they pack PC power into a laptop shell. Some of them are closer to server power than PCs. The problem is, there's better options. A Macbook Pro can be specified with an intel i9 processor and 64GB RAM - it's expensive (from £3799), but possible. A Lenovo X1 can be had with an intel i7 which can boos to over 5GHz, and have 64GB RAM also. Both of these are far lighter than a traditional mobile workstations, and can do everything a mobile workstations would be needed for. All for the cost of some mobile workstations, and they will have better battery life.
The Future of Mobile Workstations
I can no longer see the need to buy new mobile workstations. Everything can be put together in a much neater package, and one which isn't intrinsically ugly and heavy. I wouldn't buy one myself anyway, and I certainly won't be looking to add any more to my IT inventory. Future developers will have something much nicer to work with.
That being said, there's a good chance that they will shift to allow memory sizes of 128GB or more RAM to be added to them. They will become mobile data centres for folks who need to be able to access a lot of the data production may have, but where they aren't going to have the connectivity to get that volume of data from the cloud. If a lot of memory is needed, and needed on the go, then this may be the only option. Stuff an i7 or i9 into one of these bodies, and load it with 128GB RAM. That can be the only direction these devices go.
Whether or not mobile workstations do die out as a concept is largely irrelevant. I simply can't see a reason to have them. The health and safety (yes, really!) aspect of their existence is serious. They are heavy, and shouldn't be carried over any relatively large distance. There's far better options which are far safer. If you are considering getting one, give serious consideration to something much more slimline. Your back will thank you, and you'll look like someone from the 21st Century, rather than from the 1980s.