I already posted this to Bugbear Community's forum, you can find original thread here:
Bugbear Community - Coming tracks (based for ...)[community.bugbeargames.com]

Oh.. and what member of Bugbear said:

Originally posted by Olli Teittinen:

Shouldn't read too much into those, guys. :)

Sure, some of them are wips but a lot of them are versions of each other or test tracks that aren't worked on anymore.

And small warning, English isn't my native language so there'll be some typos. :)

[number][letter] (example: 5b) Same level, another route (not the same as reverse)
[number][letter]_rev Reverse of same track (not always)

• Forest5 and Forest5_rev (Tarmac 1)

• Forest7 and Forest7_rev (Tarmac 2)

• Forest0 and Forest0_rev (trackcameras)
  
• Forest1, Forest1b, Forest1_rev and Forest1b_rev
  
• Forest6, Forest5b, Forest6_rev and Forest6b_rev

• Forest2
  
• Forest3
  
• Forest4
  
• ...

+ different variations (?)

• Sandpit1, Sandpit1_rev, Sandpit1b and Sandpit1b_rev (Sandpit 1)

• Sandpit6 and Sandpit6_rev (Sandpit 2)

!Attention! In files Sandpit6 download screen image is named "..*..sandpit0..*..". Sandpit0 was old #6Update track and new (30.June) update track is Sandpit6

• Sandpit4, Sandpit4_rev

• Sandpit0 (old Sandpit6 track, maybe they'll use this name later?)
  
• Sandpit1a
  
• Sandpit2
  
• Sandpit3
  
• Sandpit4a
  
• Sandpit5
  
• Sandpit7
  
• Sandpit8
  
• Sandpit9
  
• Sandpit10
  
• ...

+ different variations (?)

!Attention! In SteamDB Sandpit0 has explanation text "Sandpit10". But Sandpit0 is old version of Sanpit6.. right? Confusing.

Image from SteamDB:

(Found from files "data/property/settings/trackcameras")

• City1, City1_rev, City1b and City1b_rev
  
• City2, City2_rev, City2b and City2b_rev

(Found from files "data/property/settings/trackcameras")

• Racing1, Racing1_rev, Racing1b and Racing1b_rev

Maybe this is Racing-track or Stadium-track (from game files)?

• Stadium2 and Stadium2_rev (Gravel)

Maybe this is Stadium-track or Racing-track (from game files)?

• Stadium0
  
• Stadium1
  
• ...

+ different variations (?)

• Oval1 and Oval1b (Speedway 1)

• Oval2 (Speedway 2)

• Derby11_rev (Figure 8)

Originally posted by Axarator:

• Derby11_rev (Found from files [data/property/settings/trackcameras])

This is just figure 8, because figure 8 is held at the derby arena.

• Oval1_rev and Oval1b_rev (Found from files [data/property/settings/trackcameras])
  
• Oval2b (Bigger oval's 8-track version).

• Derby2 (Stadium)

• Derby3 (Small Stadium)

• Derby10 (Mudpit)

• Derby11 (Speedbowl)

!Attention! Not sure did I set right images for right derby-arenas.. derby11 has new Speedbowl picture but derby11_rev is small Figure 8. So names doesn't go logically..

-

• Derby0
  
• Derby1
  
• Derby4
  
• Derby5
  
• Derby6
  
• Derby7
  
• Derby8
  
• Derby9
  
• ...

Thanks everyone who helped with this and thanks for Errol, without your Breckfest-tool I couldn't write this text: Bugbear Community - Errol's Breckfest [TOOL][community.bugbeargames.com]

Did you find something new? Is there mistake(s)? Please tell me!