lesschumras: That isn’t surprising. The reason some Chareidim are officially registered in Yeshiva is precisely in order to avoid Army service. There is no doubt about that from any side of the debate. The issue is that many Chareidim have a philosophical and theological religious objection to serving in the Army.
So before they were legally required to serve in the Army they didn’t need to register in Yeshiva. They just went to work. Since for the past number of decades they do have that legal obligation, they avoid by registering in a Yeshiva. Now, though, they cannot work legally. Nevertheless, their religious objection to serving is stronger than their need to work.
Now they can cloak their objection to serving in the Army by technically/officially being registered in Yeshiva. If they change the law disallowing that, the Chareidim will still have the same religious/theological objection to serving in the Israeli Army. So they will need to resist it in ways other than registering in a Yeshiva. They will simply have to defy the new law requiring their being drafted. After all, their religious beliefs will take precedence. And it is the same religious beliefs they’ve had since the founding of the State (and before.)
If it means thousands of Chareidim going to jail rather than the Army, they are ready for that sacrifice. You don’t seriously expect Brisker Talmidim or Satmar Chasidim to actually being IDF soldiers, do you? Everyone knows that will never happen. Even if there is a new law saying they must serve.