Verizon
Moto X 1st Gen
Android 4.2.2 - Stock rooted
Unlocked Boot loader - not DEV edition though
TWRP 2.7.1.1 recovery
Question:
To upgrade to 5.1 do I just need to revert back to stock boot loader and do an OTA update?
Will the OTA re-lock my boot loader?
After the upgrade to 5.1 do I just reload TWRP recovery and flash SU for root access again?
First off, there is no Verizon 5.1 yet. So any 5.1 you try will be for a different model, and if you flash a full rom, it will have different radios (which don't work for CDMA that Verizon still uses for voice/3g data. If you keep your stock VZW radio files, keep in mind they will be on a different version than the rest of the rom which could cause some inconsistencies and issues. IF you do flash a FULL SBF, you will be stuck with no SAFE way to revert to 4.4.4 due to GPT.BIN/Motoboot.img (for more on this, see the link in my signature), and you'll have to wait for the Verizon 5.1 SBF to get back to Verizon's rom.
Next, to install an OTA update, when it becomes available, you need STOCK RECOVERY on your phone. The OTA also does a pre-flash check/validation of your phone before it flashes, so if anything it looks for is not what it expects, the OTA will fail. Because of that you need to be 100% stock, or very near to it.
Finally, NO, an OTA will not relock your bootloader, nor will flashing an SBF.
For more on taking an OTA, see the link in my signature on OTA Updates..
That being said, if you TRY a 5.1 rom that is out there for another model you best bet is to find one that is a TWRP back up of 5.1 installed on someone's phone, since it only updates system.img and boot.img. It may not work 100% (because part of your phone will still have the 4.4.4 files), but it will give you a taste and you could later revert back to the stock 4.4.4 which you currently have on your phone. IF you flash a FULL SBF, you might be stuck with no way to revert to 4.4.4 due to GPT.BIN/Motoboot.img (for more on this, see the link in my signature)