Well, we know they were actual churches in the area now known as Turkey. Speculation is that they might be stages any given local church could go through, but many scholars hold that they also indicate something about church history till the end of the age.

But I don't know of any Bible scholar who would suggest that they represent other religions besides Christianity, though certainly all but two of the churches had major faults. Jesus had something good to say about all but one or two of them, meaning they were all at least marginally Christian.