At what point can I rule out a programming language?

[Rigorous]

what's the furtherst goal you see?
It may be "I just want to be a web developer"
If so, then rule out things that wont get you hired. Need help qualifying those? Good luck, technology moves fast and there are a lot of hyped-up rockstart languages out there that I believe will die quickly.
Unless, of course, someone makes the under layer more efficient.

 

[Puddle Jumper]

Really I wouldn't be terribly concerned about not liking any given programming language, there are so many for a reason and there are plenty I don't like too.

Once you get more familiar with programming jumping between languages gets to be less of a big deal even if you don't like all of them. I've been working as a software developer for 10 months now and I've used nearly a dozen different languages on the job so far, some of which I really like and others I consider terrible.