I don't see this as a surprise.There is a financial impact study on the ACPA website that is garnering a bit of attention. It is very difficult to pick out relevant information because it approaches the issue from many different angles, but it makes the situation look very bad for junior pilots who according to the study will lose hundreds of thousands of dollars. It even implies they will make less money by working longer
Using a baseline of normal attrition due to retirements today versus the cost of having the membership work an additional 5 years with adjusted pension triggers, increased cost of living over an additional 5 years, more concessions (?). The list goes on. A dollar earned today is much more valuable than the promise of a dollar tomorrow. So anyone that is on flat pay, PG or affected from the additional 5% Airbus concession is going to be stuck in their financial world for longer than originally forecasted.
I also read that it looks like you are right and the mandatory retirement will cease this spring. They will be filtered back into the group with additional equipment bids.
If people are hostile about the decision, just wait to see how much fun it will be in the crew room when they are back exercising their right to work

Oh, and I wouldn't be surprised if the report is a joint effort between the Company and ACPA. Neither side wants to go down this road.