The rumor is that case H is the last mainline case of Race O Rama for this year. Why is this? Because of the lenticular Cars that are coming. These are the same diecast Cars but with eyes that "move." So it's up to you if you collect these or not, but they are coming.
Presumably, any more regular cases will be exclusive to one retailer. But remember we are still left with Mega Size, Haulers, Mater's Tall Tales, the story tellers and the Kmart Cars. Plus the next line will probably start up in the Fall and who knows what the deal will be then.
Me personally, I will likely pass on the lenticular Cars. I also happen to think it is a bad idea, but oh well.