I've heard from some people (working in computational linguistics) that today the area of formal semantics is on the decline. On the other hand, I can see many new papers from formal semanticists on their webpages. So I was wondering whether this field is "alive enough" today and whether there is a demand in formal semanticists today.
There are fewer academic jobs now compared to the 70's and 80's (in general), and the wave of "baby boom" retirements is just starting. Formal semantics is a "later" field and scholars in that field are comparatively young (in relationship to e.g. syntax). In one sense, there is little demand because it has already been filled. However, formal semantics is kind of a "niche" field, like phonology has been (there are typically more syntacticians than phonologists in a department), and for example Santa Cruz had multiple syntacticians and no phonologists so the syntacticians taught phonology until they finally hired a phonologist or two. In the really old days, it would be inconceivable that a linguistics department would not have an Indo-Europeanist, but the field changed and now few departments have them.
A complicating factor is that there it's not obvious what a "formal semanticist" is. The term "formal" is often taken to mean "theoretical", but IMO formal semantics means a theory of meaning where you can reduce linguistic utterances and their interpretations to a mathematical equation plus non-linguistic rules of logic. Many theoretical semanticists don't do that, or don't do that as much.
Demand for academic phonologists and semanticists is comparable, it appears to me. As Jlawler said, if you are a superstar, you might get a job. Otherwise, the odds are that you will need some number of related skills, for example computational linguistics or a language area, or both. This is because the best departments have one or two semantics classes at most, and the teaching load will need to be filled in with other stuff (remember: there are a lot of syntacticians out there).
You can browse the Linguistlist job listings and see what's on offer now (it will be a tedious manual slog). I found one "permanent" academic job in Scotland that is for a semanticist (others are non-academic or 1 year nonrenewable).