Assuming you're using a custom recovery (CWM, TWRP, etc.), the OTA will fail to run, and shouldn't make any changes. If it did somehow run, it would certainly remove that capability.
If you really want 4.3, I would suggest installing the pre-rooted ROM available on XDA, along with the MK3 modem and deknoxed MK3 kernel:
ROM: [STOCK ROM] Stock 4.3 MK3 ROM [ROOTED/UNROOTED] - xda-developers
Modem: [MODEM][FLASHABLE] MK3 Sprint Modem - xda-developers
Stock Kernel (no Knox): Dev-Host - stock_kernel_mk3.zip - The Ultimate Free File Hosting / File Sharing Service
modded kernel: [KERNEL][4.3/4.4/TW4.1/TW4.3] dkp - d2spr - 12/13/13 - xda-developers
That is a good question, I'm honestly not sure. Sorry.
Unless you have a compelling reason to upgrade, maybe staying on 4.1.2 for the time being is the best bet.