I'll agree with everyone else, the leves will likely reset on a global timer, not based on when you picked them up, atleast that's how it's been so far.
Now they said they were going to address the leve system, as far as reducing the 48 hour timer, that's just an assumption, but the most probable solution.
Personally, I don't mind the 48 hour timer for leves, that's 16 leves every 2 days, sounds like plenty to me, especially considering they were trying to cater to casual gamers. Now if it were to actually change to a 24 hour reset, that's fine by me too, I suppose you could atleast login to refresh your leves and exchange them for more or better rewards.
Aside from all that, here's a few possible ways they might intend to improve the current leve system.
1. Shorten the reset timer from 48hr.
2. Increase the amount of leves available during each period.
3. Seperate Battlecraft and Fieldcraft leves, allow them each 8 leves, instead of combining them. (Crafting gets a dedicated 8 leves, why not Gathering?)
There are many other possibilities, but it's ultimately up to SE to decide. Surely it can't get any worse, let's just be happy they even decided to something.