Hi LightYagami, not to worry.
Very few deaths occur as a result directly because of activities that take place here

I could certainly imagine wondering about that if I didn't have the... luxury(?) of visiting this forum as much as I do (it's really a very friendly and helpful community, and probably the best place to get an 'informed' answer to that question).
To answer your question, there's not yet any development of Android L for the Note 3 (particularly the T-Mobile variant) that is yet available for public use. I have no idea when that will become available, but as soon as it is, I would imagine that the place to find it would be in one of the top threads (i.e. most discussed) in either the Android Development or Original Android Development forums.
Personally, I prefer to stick to TouchWiz-based ROMs in order to maintain proper function of the phone's native features. The ROM versions based on Samsung's TouchWiz are limited by the firmware versions that are released specifically by T-Mobile. For example, you may have seen that Sprint Note 3's are receiving a new version of firmware that will bump them up to 4.4.4. T-Mobile users however, just received our
third update to version 4.4.2 (currently the firmware version ending in NF9) and there is talk that we'll receive yet another update within a few weeks that will remain on 4.4.2 (but not likely any less "current" than the version of 4.4.4 released by Sprint). Anyway, of the TW based ROMs, my personal favorite is called Tweaked, which I feel pretty confident that anyone who feels negatively about TouchWiz would change their opinion after trying out Tweaked for a bit.
There are also ROMs developed that aren't based on TouchWiz but instead based on the Android Open Source Project (for example), which many people prefer because they are variations of pure 'vanilla' Android rather than Samsung's TouchWiz skin (this is generally my preference on devices that don't have as many custom specialized features as the Note 3, which are generally sacrificed to some degree when using a ROM that isn't based on Samsung's skinned version of Android). These ROMs generally are based on a newer version of Android, their development being limited by the point that the AOSP is at on our device.
Hopefully that answered your question and gave you some kind of idea of what you can expect. To summarize, Android L will likely come to the Note 3 relatively soon, but no preview suitable for public use is yet available. Not sure if my reference to various ROMs is something that you're familiar with, but you can learn quickly by browsing around the forum