A while back I came across this:
This is from somebody did art stuff for LEGO Battles and the sequel LEGO Battles: Ninjago. About 22 seconds in you can see a clip of two knights fighting that doesn't seem to belong to either game - it's not Ninjago, but the art's definitely ahead of that in the original LEGO Battles. So I emailed him a while back and asked him about it.
Turns out it was actually an art test for a LEGO Battles 2 before it became mostly Ninjago themed. Also, the switch to the isometric perspective was part of the game even in those early LEGO Battles 2 days.
Also, LEGO Battles: Ninjago was going to have its cutscenes rendered in a cel shaded style (3D made to look 2D), and while it was cool, it was made to look more like the TV show for consistency.
He was also the resident LEGO expert in the dev team, and was glad we'd picked up on all the references to old LEGO stuff. I also showed him Aaronburner05's Gemma mod for LEGO Racers - he liked it, said he loved LEGO Racers.
One more thing - we've found more info on that 2009 LEGO Racers game mentioned in the OP since that post was written, you can read about that here if you haven't already: