Maybe at the moment, but not by the time he's 30. It will go the way of people turning in a resume with "HTML" experience. It'll be expected as a minimum.
A couple things make your scenario less likely than you might believe.
1. Salaries rarely go down once you've landed the job. So if he can get an $70k job now and get a $5k raise each year for the next 4 years that puts him in a pretty good spot to switch jobs and jump to the $100k.
2. Depending on his desire he could leverage his programming + design skills in a unique way that allows him to get to $100k from freelancing, building products, etc. Learning the backend is a stepping stone not the destination, but combined with #1 above means earning an extra $20k on the side is very doable.
3. I doubt that the ability to build enterprise applications out of ruby/python/js will ever be seen as bottom tier office work. People can't figure out how to work their own printers at work, I don't think we'll see these people suddenly learning how to build enterprise applications. Again, even if that is the case, sit tight and your salary probably won't decline as long as you don't leave the job.
Agreed, if he could somehow get the $70k now. He mentioned no existing backend experience, so that was my point about getting this future backend ruby job. One thing in his favor is that people are throwing money at it now, and he might be able to trick his way into such a job with just a Code School course or two under his belt. This would be the "job hacking" way to accomplish it, at least.
Yes, in 3 to 4 years, programming in Ruby or Python will be considered a skill that entry-level positions should have. In fact, I envision a future in which even the doormen of a building hook into hackernews APIs to verify the account standing of visitors.
Now, now... I can accept snark for snark. Entry level programmers, not entry level people. I already expect any resume for a direct-from-university applicant to have at least "HTML, Ruby, Java, Python". It's basically a bare minimum for a programmer these days. You don't have to know Ruby specifically, but it's a red flag if you only have one or two languages. If they don't have a lot of depth, they at least need plenty of breadth.
Entry level programmers will continue to have things taught in university - seemingly more Java than anything. Changing the scope of your comment to mean "entry level programmers" and not just "entry level people:" the kind of person with very cursory HTML knowledge is different than the kind of person with a little knowledge of Ruby. HTML is a mundane system of syntax, approachable by even a marketing major at a party school. Being able to write a little Ruby is a far different beast as it requires some ability to handle logic and referential extrapolation - even if most Ruby coders can't seem to 'hello world' without installing a few gems.
