Until the second world war the language was quite alive all over Gotland. Though it started to loose speakers especially in the north, first close to the only town, Visby. The south of Gotland has always been strong when it comes to the strength of the language.
Even in the 50´s and 60´s there were a lote of Gutnish speakers. The 70´s saw somewhat of a revival of the language and in the 80´s the situation was still stable. Though the signs were visible in the 90´s it was not until shift of the millenia that we saw the heavy decline of Gutnish as a spoken and used language.
When this stage has been reached other measures have to be taken. I believe that major efforts have to be put into making Gutnish into a proper written language.