Are there any educated guesses as to who the whistleblower might be?

[babylonsister]

I believe I heard or read that Dan Coats, former DNI who resigned (or was fired), could be.

[meadowlander]

1. Him or his deputy who resigned within a few days - Sue Gordon.

https://www.bloomberg.com/news/articles/2019-08-08/u-s-deputy-intelligence-director-is-out-after-trump-meeting

[jcgoldie]

2. Sue Gordon?

The way Coats asked for her resignation interrupting a meeting seemed very odd to me at the time and occurred immediately between the Zelensky call and the whistleblower complaint.

[RockRaven]

3. I don't think it is Coats or his deputy who also resigned. I bet it is someone who most people

have not heard of.

[klook]

4. Stephen Colbert offered his prediction last night

It comes toward the end of this video, but the whole five minutes of stuff from various late-night monologues is worth checking out:
https://www.usatoday.com/videos/opinion/best-of-late-night/2019/09/25/colbert-reveals-impeachment-whistleblower-best-late-night/2441080001/

[Catamount]

6. Thanks, that was awesome! (Jokes)

I also suspect Dan Coats, or his deputy and found his resignation telling, and then his interruption of the meeting to tell his deputy to resign, almost confirming this notion. However I guess it could be any decent patriot.
Hope we find out sooner than later. 😁

[obamanut2012]

5. I think Sue Gordon or Dan Coates for sure n/t

[dewsgirl]

8. I saw several tweets where the WB was referred to as female.

I believe Dan Rather is where it started.