Join Date:Joined: Mar 2013
Sony's official product page for the ZL states that the next update will be 4.4. But it won't be soon, remember 4.3 has only just arrived on all regions after about 1.5 months of waiting between the first and last country to receive it.
Also, comparability with 4.3 was built into apps about the same time the update to 4.2 was released, then 4.3 was teased and it took 3 months for them to start rolling it out, badly.
While yes, we will be seeing 4.4 on our phone, it will not be soon, it will likely arrive a month or so after the next flagship hits stores.