Yes, Lightroom mobile will be able to add the raw files to the collections.
However, it will only sync preview file from your iPad to your desktop computer. It will not sync the raw files to your computer.
Hope this helps.
You might want to look into how Lightroom mobile really works. It is NOT a good solution to ingest raw files as it simply doesn't support that. It is also not a mobile version of Lightroom at all. If you are looking for that you will be deeply disappointed. The way it is supposed to work is that on your desktop machine, you set a number of images in a collection to sync with mobile. Lightroom on your desktop will turn the raw files on the desktop in that sync into a lossy compressed dng, generally at a lower resolution than you have. Those dng files, which are raw files in a sense, are then synced to the mobile app. On the mobile app, you can now do a subset of the editing you can do on the desktop, and those edits are synced back to the original raw files. So basically you can get a mobile editing solution for your raws synced back and forth to your desktop machine. It's nice to sit on the couch and work a bit on your images. That's about how useful it is. It is not color managed, it is not a raw ingestion solution (i.e. you can't replace a laptop with it on a trip), it is not a full editing solution, it is not a key wording solution, it is not a way to get your images online easily, etc, etc. It IS a fun little way to casually edit some images that are really stored on your main machine.
If you are only thinking about adjustments, I don't think the new iPad will make a difference to you. LrMobile suits a workflow that loops from the computer, out to mobile devices and web browsers, and then back to the computer. For me its value is for showing pictures (LrMobile obsoleted the various portfolio apps I've bought), for reviewing pictures and assigning ratings and flags when I'm away from my desktop, and for broad adjustments and cropping. While it would be good if the iPad had colour management, it really doesn’t matter. Using LrMobile for Quick Develop-style adjustments means that when you are back at the desktop you're able to spend that time on fine tuning.