Is there a plan to have abook for Joomla 3.X? YES :-)
Will Abook for Joomla 3.X be available soon? Ehm, we hope :-/
Federica is working to complete migration rewriting of code to allow Abook working on Joomla 3.X.
Abook aim to be a well-written code (shhh! don't tell this to Federica or she blame me!), but writing a code that follow all rules of the Joomla Framework isn't a very simple trip.
Documentation of Joomla 3.X Framework is not completely written yet, or at best is without examples and without explanations. Then the only way to know how to use a function or a class is to search in other components if it's used, and try to understand how it works ( a sort of reverse engineering).
Joomla Framework is full of very good things for developers, but they are changing some things, because Joomla 3.1, Joomla 3.2, and so on until Joomla 3.5, are STS versions (Short Term Support).
"What's?". Yes, only Joomla 3.5 will be considered stable, in the meantime things can change, and things are changing. A silly example: the Joomla 3 Framework function that allow to choose the article publication state, writes a number in a column of a table in the database. Obviously this column must have a name, like all other columns in every tables. Since a sometime ago this name didn't matter, because the smart framework accepted any name, Federica has built her table as she preferred. But now the framework expects to have this column named "published".
Now, should Federica rename the table column? Or she has to rewrite the function? Or may be that it's better to wait, to see if they return to a better solution to allow to choose any name?
All of this, summed to the very little free time that Federica has, makes the process of releasing Abook for Joomla 3.X a sort of stalagmite's dripping.
"Ok, but when will be available abook?". The answer is....: About 90% of Abook is ready (maybe something more).
Then, be patient, Abook is coming!