Opera may have given up on Presto, but there are people who haven't. In fact, there are some who would like to see the layout engine released as open source.
There's a petition going, it's got less than a couple of thousands of supporters for now, but there are talks of an open source Presto in various other places.
Of course, these types of talks and petitions were to be expected, they usually don't go anywhere. But there is reason to hope, while Opera hasn't said anything on the matter, it's actually thinking about it.
"It may be that the Presto code will be released, but for now it's all hands on deck making the transition. So far, it looks good," Håkon Wium Lie, the new CTO of Opera, said in a WebKit mailing list.
That's hardly a confirmation, but it does show that Opera is at least considering it and at the top level.