I think that learning languages is not a bad idea if:
1.) The cost is high enough, meaning that sufficient amount of coins are taken out of the game (2,5++ gps)
2.) You can only learn one (max two!) new languages, with intelligence limits on your learning capacity, varying from language to language.
2a.) People with intelligence of less than 10 would not be able to learn any more languages at all.
2b.) People with intelligence of 10 or more would be able to learn 1 new language, as long as they have sufficient int for the language they wish to learn.
2c.) People with intelligence of 18 or more would be able to learn two new languages, but the gp-cost would be increased for the second language
2d.) Languages would have specific requirements in terms of intelligence (eg. Human* 15 int, Elven 17 int, Orcish 10 int, dwarven 12 int.. so and so)
3.) Learning languages is not only the result of you PG'ing it, but also actual time spent playing the char, meaning that every once a while you get a swirlie in it, but mastering the language should take quite a while (imo).
The reason for that is that all racial languages are not equal anyhow. It would be incredibly easy to get a human or elf on your side to interprete what the others are discussing if you would be expecting such situation, whereas finding a goblin, gnome or a fairy would be near impossible. This means that some racial languages are more useful than others. Besides, the fact that players know that the other side is completely unable to understand what they are saying is rather unsatisfactory in my eyes as well. If you talk german in front of me, even though I am not a german, I may be able to understand even if you do underestimate me.

In illarion, this won't be the case.
*Human-example may seem high, but this is simply to make it as less-obvious-choice for chars as a second language, as it would be if the requirement was ~10.
Edit:
One possible thing would of course be to allow anyone with int 10 or more to learn a language, but install a cap on learning it which depends on your intelligence vs. the required intelligence of the language. Meaning that, say.. your intelligence is 11 and the language you wish to learn requires 15, you can only learn X%-of the max skill.