I would assume that there will be more older (2000s and earlier) outtakes since they used to write way more songs for one album than they do nowadays or it will at least be fairly balanced between older and newer stuff.

I also don't think the songs they actually put on recent albums are necessarily an indication of what the outtakes from those session might be like, because Jon in particular is quite bad at picking out which songs are the best and most worthy of being put on an album (or chosen as a single). A song like Limitless makes it onto an album because it fits a certain formula and Jon thinks it could do well commercially, while a song like Luv Can is quickly downgraded to nothing but a bonus track.