The retraced Lulu material appears exclusively in sets 1 and 2. The other four are just fine, although you are correct that the first two volumes comprise the 1940's material. I'm not entirely certain that ALL of set 2 is retraced. Alas, the D&Q series has ended prematurely after 3 volumes.
The third and final (for now) volume of Drawn + Quarterly's full-color hardcover Little Lulu books has been out for a bit. I'm sad that the series has been put on hiatus just as it was picking up some steam.
Alas, the current copyright holder of the Lulu entity, who has no plans to do anything with this property, declined to renew the license. Their reasons are unconvincing and a lot of hard work done on the fourth, fifth and sixth book has bitten the dust.
I'm guessing the "current copyright holder" is also the company we have to thank for blacklisting certain stories where Lulu and her friends are playing indians.
I may be wrong, but I seem to recall reading that was a D&Q decision. Certain staff members didn't feel that more stories needed to be in circulation that required apologies.