There are “few chances” of Lubuntu becoming an “official” spin of Ubuntu 10.04 according to Lubuntu developer Julien Lavergne. 
The project, which provides the lightweight LXDE desktop as its base, still has many of its important packages missing from the Ubuntu repositories, its default file manager is still in alpha and many ‘core’ applications of the Ubuntu experience (such as network manager) have yet to receive LXDE equivalents.
In daily usage Lubuntu remains the lightest Ubuntu flavour ” out performing even ‘low end’ choice Xubuntu.
So, for now at least, Lubuntu will remain that cousin who couldn’t make it to the party. Here’s hoping it managers to get its’ thang on in time for October.