For doing that is required a script; not a command. As I don't know which operative system you have, I am going to use a bash script in my Linux system (in Windows the equivalent is a bat file) and by using only shapefiles.
#!/bin/bash
for i in *.shp
do
ogr2ogr -t_srs EPSG:4326 out_data/$i $i
done
The above script (named as convert and running with ./convert) worked well and it projected all the shapefiles in the current directory to ESPG:4326 and it saved them with the same name in the out_data directory (out_data must be created in the directory where is running the script).
The following image is the working directory with diferents shapefiles and raster (included the script and out_data):

Directory out_data after running the script (the shapefiles were loaded to QGIS with the fly projection activated for verification purpose). It only contain shapefiles with the desired projection.

Editing Note:
I didn't know the bat sintaxis but I found it. It's precisely in one line command. The correct sintaxis is:
FOR %%i IN (*.shp) DO ogr2ogr -t_srs EPSG:4326 "out_data/%%i" "%%i%"
The above bat file (named as convert.bat and running with convert) worked well and it projected all the shapefiles in the current directory to ESPG:4326 and it saved them with the same name in the out_data directory (out_data must be created in the directory where is running the bat file).
Successful execution of the bat file in my XP Windows System:

ogr2ogr -t_SRS EPSG:4326 "ESRI Shapefile"
– user30184 Mar 13 '15 at 14:50