Launcher got stuck in loading screen

Yes, see MCL-5534

I found the cause. (In just my case)
The cause is in the Users folder.
cmd> mklink /j C:\Users U:\
But, I want stay this setting in windows.
----------------------------------------------------------------------------------------------------
C:\>dir User*
C 드라이브의 볼륨에는 이름이 없습니다.
볼륨 일련 번호: D841-AF5E

C:\ 디렉터리

2017-04-01 오후 04:25 <JUNCTION> Users [U:]
2017-03-31 오후 11:52 <DIR> Users_legacy
0개 파일 0 바이트
2개 디렉터리 70,531,215,360 바이트 남음
----------------------------------------------------------------------------------------------------

Success.
cmd> mklink /d c:\Users u:\

Is this still a concern in the current Minecraft Launcher version 2.0.1003 / 2.0.1004? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.

Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. It will be reopened it as soon as the requested information has been delivered.