Are there any good reason to learn languages such as Ada and COBOL? Are there any future in programming in those languages? I'm interested in those languages and i'm currently learning them just for fun.
Its always worthwhile learning new languages. Even if they're never useful to you professionally chances are they'll teach you something about programming you didn't know before or at very least broaden your outlook.
As for prospects from a quick bit of reading around it seems ada is still somewhat in favour for critical systems in the aviation industry and Cobol still has its place in business. I know an engineer in his mid 20's who writes all his code in fortran77 as that's what industry wants!
While the number of employers looking for these languages might be low, because there are a limited number of people who know them the salary for developers who specialise in them can be quite high. When mission critical apps developed in them could cost millions to replace having to pay more than usual for a coder to maintain the existing system is easily accepted.
Ada is used in the aerospace/defense industry. COBOL is used in the financial industry. Fortran is used in engineering. The question "is there any future" is borderline subjective/argumentative since all of those languages are still in active use.
Cobol and Algol are both still in widespread use. You won't find them running on your latest and greatest tech firms, but you can bet your car insurance company process' claims on it. Your health insurance company most certainly uses it. Reports of Cobol's death have been highly exaggerated.
You will find difficulty in colleges and places that will actually teach you Cobol or Algol. So finding developers for these so-called dead languages is getting harder and harder. Very tough to tell a kid coming out of high school that has been programming in Java, iOS, and Perl for half his life that Cobol is where the money is at.
Cobol/Algol developers are becoming harder and harder to come by, so if you have that language in your back pocket, it is only going to help you out. Algol is a lot harder of a language in my opinion to get good at. You can teach anyone with half a brain how to program in Cobol.
These languages are not going away any time soon at all. As long as companies like IBM and Unisys provide compilers for them on the mainframes, they will continue to thrive. So grab a book and an open source compiler and brush up. Plenty of people out there looking for Cobol/Algol developers.
Fortran is old, but is used in scientific programming. Ada is the basis for VHDL, a very important language in electrical engineering. You could also say that C is "old", and it's used pretty much everywhere.
Many of these 'old' languages are actively in use today. Lisp for instance is gaining popularity again in the form Clojure. Smalltalk is becoming popular again with the Seaside MVC framework.
Much like learning Latin, it can be intriguing to understand where and how many English and other current languages' words had their roots. Also, if you know Latin and valuable new books/papers/scrolls are found that need translation, you suddenly become valuable too.
Honestly, I'd say learning them is great for a historical perspective, especially if you're a language designer, but not very much else.