? ULMB 2 is just a firmware update, if other 360hz monitors can have it, so can the AW2521H

That will not happen as that would require new hardware.

That's just absolutely egregious considering the price of the monitor. Dell should do better.

This one is not user upgradable either: monitor 

I have not seen any firmware for the one you have, so chances are high it's not user upgradable either. A lot of it depends on the G-sync module used in it.

Not all monitors have firmware that is user upgradable. 

Firmware is normally released for consumption if there is an issue to fix or a feature to unlock.

AW2521H doesn't have any firmware updates because no fix has been needed and no new features were announced for it.

This monitor is absolutely capable of receiving a firmware update. 

Nvidia's stated limitations for ulmb vs ulmb2 was simply monitor response time. Not gsync module version or any other hardware limitation. The aw2521h has no pixel response limitation and has no other Nvidia described limitation. Therefore, no hardware changes are required.

Using reasoning such as "I've not seen any firmware [for your monitor]" doesn't mean it's incapable of receiving a firmware update. 

From Dell's support page:

"Firmware updates are released to resolve issues or improve the functionality of Dell monitors." (Just like I said)

https://www.dell.com/support/kbdoc/en-us/000131809/steps-for-updating-the-firmware-for-your-dell-monitor

And gsync modules are NOT a requirement for a monitor to receive firmware. And Nvidia didn't mention any gsync module version as a ulmb2 limitation. Just that gsync is required.

In that case, looking forward to the firmware update. Keep us posted, so we can provide better information to other customers who might have the same question.

I forgot to mention, you don't have to believe me when I said that a lot depends on the G-sync module.

You can see this post for the official Dell statement regarding firmware updates for monitors that contain G-sync modules: Post 

"Currently all Dell monitors that have the Nvidia G-Sync module can only be firmware upgraded via the Dell Service Center. But, you can only get one of those via an exchange."

I own this monitor and i would like also to get the firmware update because is one of the best 360 hz gsync monitors out there, its not a matter of hardware is a matter of cost money and profit for dell, if this model dont get the firmware update i will switch to other brand.  

Exactly what I was thinking! It's a perfectly capable and up to date monitor that's not given proper support. And if you look at the stats, the Asus AQN monitor which boasts 1440p and 360hz has 1.3ms of grey to grey response time while the 2521H has 1.8ms (both using Extreme overdrive) despite it's "older" panel! Now what's the real reason for the Asus monitor to get the update first despite being 2 years newer and having negligible difference in tech? That's for you to find out!

Source for AW2521H response time 

Source for Asus AQN response time