Maria is correct. You can still enter the Cathedral via the South Transept (Plaza Praterias), to tour the inside of the 'naked' Cathedral (all the wood is removed). This is significant, as pews and confessional boxes were not added until the 1600s. So, if you see it "naked," you are seeing what the earliest pilgrims saw... minus the scaffolding and plastic sheeting of course...
You can also climb the stairs to perform the traditional abrazo or embrace of the Saint behind the main altar. Coming down from this, you can queue to go down into the crypt to venerate the relics of the Saint in the silver casket under the altar.
As regards WHEN the Cathedral will be fully functional and reopened, earlier in August, Don Segundo, Dean of all things pilgrim related for the Cathedral was interviewed by La Voz de Galicia. In that interview, he was asked the same question. His reply was that he hoped the Cathedral could be fully reopened by "...early in 2020..." That is all I know. I am just repeating what I read.
One should presume that this date, like others, will slide somewhat. Renovating the Cathedral is a HUGE undertaking. Surprises will occur. About the only thing you can take to the bank, is that the Cathedral (and Botafumeiro) will be back online by 1 January 2021. This is the first day of the coming Holy Year.
Hope this helps.