Have you plugged it in? Do you like the sound of it?
If you aren't going to be performing, I would wait on worrying about pickups until you upgrade to a better 'ukulele (Kalas are not bad, you just might want to consider putting the money that you would spend on upgrading pickups towards a better uke).
If you are going to perform, I don't think there are any problems with the Kala pickups, so again, I wouldn't worry about upgrading pickups until you have a different 'ukulele.
I play a Hilo passive on my Kamaka. When I had it put in I knew that it wasn't the best, and I had to have it adjusted so it would work on my uke, but now it sounds nice to my ear.