H4 visa dropbox approval chance, H1B valid for 3 months only

Hi all,
I’m on H1B and my recent extension was approved only till Mar 2020. This is my first extension. My wife (currently on H4 dependent visa) has to travel to India in Jan 2020.

Since our prior visa expired in Nov 2019 i believe my wife is eligible for dropbox option. Has anyone faced similar situation in recent past? Can anyone suggest what the chances are for her visa to be extended till March 2020 via dropbox option? Will it be a problem since there is only two months of time left (till March 2020)?
Also can the dropbox be done with copy of my approved I129 petition or should my wife wait for her I539 to be approved?

Thanks a lot in advance!!

There will not be any problem to get H4 visa. Many users have done that and it will be fine.
They need a copy of your H1B approval notice, your copy of Visa.
No need to wait for her I-539 approval, if going for stamping.

But, frankly, I would suggest to wait a month or ask your employer to file the extension in premium and go for stamping with new approval that is beyond March 2020.