There's really no universally agreed-upon "pronunciation" of wwwwwww, even among native speakers. (It would be like asking how you "pronounce" a smiley or something.)
the only time I've heard it read aloud was as (笑), or "kakko-warai." Sometimes someone would read "w" as that, just so it's understood to the listener that it was some form of the Japanese "lol" variant.