I know both and use "so so, la la" more often.

So lala (umgangssprachlich: einigermaßen; bedingt gut: das Wetter ist so lala; es geht ihm so lala) So so la la kenne ich nicht. So lala (colloquial: somehow e.g. good/bad, good only to a certain extent, meaning not really great: the weather is so lala, he feels so lala) So so la la: I have never heard that form.

As you see from our answers, a colloquial expression like this and its uage is highly regional, specific maybe also to social groups or generations. As for "is it up to date": To me it feels just slightly old fashioned. I don't hear young people saying it. The'd maybe rather use "eh, geht so" to express the same meaning. But then again... that's my experience here in Vienna. Somebody from Hamburg might tell you something different.