I think that's where some classic teams could work rather than creating an entire era. Using your 2008 example, a lot of people would be familiar with Tamika Catchings, Lauren Jackson, Lisa Leslie, and Candace Parker but I bet familiarity drops off a cliff shortly after that. So it seems like it'd be a lot of effort for 2K to create an entire league when most gamers likely won't recognize many players beyond the top 10 at the time.
On the flip side, if you just went ahead and created some standalone classic teams, I could see some draw among people who'd be interested in choosing a 2008 Sparks squad Lisa Leslie and Candace Parker or the aforementioned Cynthia Cooper/Tina Thompson Comets.