Oh...that is way too vague.
The Gospel is always relevant. However, people will never understand their need for it unless you find a way to interact with them. When we separate ourselves from the world to the extent that we no longer interact with unbelievers on a regular basis we simply remove our opportunities for evangelism.
To ME, what is meant by being "relevant" is really just, "I think we should hang out with people who need God."
The fear is, though, that fraternization will produce fellowship in such a way that the Christian becomes less so and the unbeliever sees nothing different to desire. Tricky little problem, because evil communications DO corrupt good manners. At some point, some corruption may be necessary to allow the church to do what it was meant to do.
In other words: We need to get our hands dirty.
That's what I think it means to be relevant. Meet needs. Like Jesus did. Without participating in the behaviors and lifestyles that destroy people--or offering tacit approval of the same. And then the Gospel can be shared in a way that is truly meaningful.
Perhaps the church should challenge its constituents to "Invite a sinner for dinner." (a non-relative, perhaps, to make it a little more difficult?)

(Instead of inviting them to church.)