The quick answer to this is Yes and No.
No is the answer if you are looking for a dedicated iPad app that our newer V-Mixers have (such as the M-480, M-300 and M-200i).
To ensure the application of wireless technology remains at the high level of reliability required for professional operation, we have chosen not to implement an iPad Remote app for the M-400 and M380 V-Mixers at this time. Considerations include harnessing the USB technology from the 2007 design as well as ensuring stable past and future version updates. We will however continue to consider this application.
Yes is the answer if you use a remote desktop application which in fact can work on an iPad as well as other tablets/laptops.
In this case you can use a VNC application on your tablet in combination with the M-400 Remote Control Software (RCS) on Mac or PC (Win). This can be downloaded here:
https://proav.roland.com/global/products/m-400/downloads/
Search the iTunes App store for VNC or Remote Desktop control apps such as VNC Viewer and iTeleport.
The RCS will run on your computer and you will essentially connect to it through a window on your tablet and control remotely.