I am thinking that announcing this feature may be a tactic to win back consumer trust or in the least attract new customers who are not familiar with the potential buyout.
It hasn't been purchased yet; the buyout deal is yet to go through AFAICT.
So I guess this an attempt to add value to push the deal through.
Opera has a long history of adding innovative browser features. There's no reason to think that this has some kind of ulterior motive related to a rumored sale.