Hamechadesh is reporting that Rav Shapira said at the shiva call that he paskened for his students and for anyone who asked him that it is assur, prohibited, in no uncertain terms, to go to Meron on lag B'Omer.

Rav Shapira said that the Torah tells us pikuach nefesh takes precedence over everything else. You can eat every type of treif food in a pikuach nefesh situation. We eat on Yom Kippur if it is pikuach nefesh.It has been proven that on Lag B'Omer this place, the Kever Rashbi in Meron, is a place of pikuach nefesh, and it is therefore completely assur to go there on Lag B'Omer. Someone who wants to go can go 3 or 4 days before Lag B'Omer, or after Lag B'Omer, but on lag B'Omer it is too dangerous and a person cannot put himself in that situation of danger.

It is unclear to me if he paskened this way for people prior to Lag B'Omer (and thereby perhaps prevented some other people form being in danger), knowing from the past that the danger is real even though no significant tragedy happened before, or if this psak was post-Lag B'Omer because of what happened and is meant only for future years. 

If it is for future years, it seems like the psak might be premature. it seems highly likely that the situation will be altered by new safety measures in coming years and maybe it will be deemed safe. It might remain unsafe, even with coming changes, but this is something that remains to be seen.